* helpers: lockfree lookup of nobody user on linux and darwin

This PR continues the nobody user lookup saga, by making the nobody
user lookup lock-free on linux and darwin.

By doing the lookup in an init block this originally broke on Windows,
where we must avoid doing the lookup at all. We can get around that
breakage by only doing the lookup on linux/darwin where the nobody
user is going to exist.

Also return the nobody user by value so that a copy is created that
cannot be modified by callers of Nobody().

* helper: move nobody code into unix file

This PR adds a jobspec mutator to constrain jobs making use of checks
in the nomad service provider to nomad clients of at least v1.4.0.

Before, in a mixed client version cluster it was possible to submit
an NSD job making use of checks and for that job to land on an older,
incompatible client node.

Closes #14862

This PR removes the assertion around when the 'task' field of
a check may be set. Starting in Nomad 1.4 we automatically set
the task field on all checks in support of the NSD checks feature.

This is causing validation problems elsewhere, e.g. when a group
service using the Consul provider sets 'task' it will fail
validation that worked previously.

The assertion of leaving 'task' unset was only about making sure
job submitters weren't expecting some behavior, but in practice
is causing bugs now that we need the task field for more than it
was originally added for.

We can simply update the docs, noting when the task field set by
job submitters actually has value.

* Makes service tags wrap and look like tag items

* Add a little vertical spacing and changelog

* Put client before tags

* Force tags list to new line

* build(deps): bump github.com/opencontainers/runc from 1.1.3 to 1.1.4

Bumps [github.com/opencontainers/runc](https://github.com/opencontainers/runc) from 1.1.3 to 1.1.4.
- [Release notes](https://github.com/opencontainers/runc/releases)
- [Changelog](https://github.com/opencontainers/runc/blob/v1.1.4/CHANGELOG.md)
- [Commits](https://github.com/opencontainers/runc/compare/v1.1.3...v1.1.4

)

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* build(deps): bump github.com/prometheus/client_golang

Bumps [github.com/prometheus/client_golang](https://github.com/prometheus/client_golang) from 1.12.0 to 1.13.0.
- [Release notes](https://github.com/prometheus/client_golang/releases)
- [Changelog](https://github.com/prometheus/client_golang/blob/main/CHANGELOG.md)
- [Commits](https://github.com/prometheus/client_golang/compare/v1.12.0...v1.13.0

)

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* build(deps): bump github.com/mattn/go-colorable from 0.1.12 to 0.1.13

Bumps [github.com/mattn/go-colorable](https://github.com/mattn/go-colorable) from 0.1.12 to 0.1.13.
- [Release notes](https://github.com/mattn/go-colorable/releases)
- [Commits](https://github.com/mattn/go-colorable/compare/v0.1.12...v0.1.13

)

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* build(deps): bump github.com/google/go-cmp from 0.5.8 to 0.5.9

Bumps [github.com/google/go-cmp](https://github.com/google/go-cmp) from 0.5.8 to 0.5.9.
- [Release notes](https://github.com/google/go-cmp/releases)
- [Commits](https://github.com/google/go-cmp/compare/v0.5.8...v0.5.9

)

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* build(deps): bump github.com/miekg/dns from 1.1.41 to 1.1.50

Bumps [github.com/miekg/dns](https://github.com/miekg/dns) from 1.1.41 to 1.1.50.
- [Release notes](https://github.com/miekg/dns/releases)
- [Changelog](https://github.com/miekg/dns/blob/master/Makefile.release)
- [Commits](https://github.com/miekg/dns/compare/v1.1.41...v1.1.50

)

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* Explicitly update X-axis whenever xScale changes

* Changelog

Signed-off-by: Hemanth Krishna <hkpdev008@gmail.com>

Jobs not requiring any network resources should be allowed
even when the network fingerprinter is disabled.

Fixes #14614

When community members comment on long-closed issues, there's a number of
failure modes that make for a bad experience for them:

* Their comments are often missed entirely because notification settings make it
  impractical for most developers to read comments on inactive issues.

* In our experience, the problem is only rarely a regression; because failures
  are complex, totally different code paths can result in symptoms that initially
  appear to be the same but turn out to be completely different under close
  examination. This is particularly the case for issues fixed in very old
  versions (sometimes 2 or more years old).

The Terraform core team uses a bot that locks issues after only 30 days. But
because we typically close issues automatically on PR merge but don't have
rolling releases, it'd frequently happen that unrelease fixes will have locked
comments, which isn't a good experience either. I've looked through the pace of
releases since Nomad 0.9.0 and the longest window between releases was 3
months. Set the window for the lock bot to 120 days to give us plenty of
breathing room so it doesn't feel like we're shutting down discussion
prematurely.

* docs: clarify nomad vars vs vault

I think we should make the difference in root key management between
Nomad and Vault clear in the concept docs. I didn't see anywhere else in
the docs we compared it.

I also s/secrets/variables everywhere except the first sentence since
the feature is intended to be more generic than secrets. Right now it's
more of a compliment to Consul's kv than Vault due to root key handling
and featureset.

* Update website/content/docs/concepts/variables.mdx
Co-authored-by: Tim Gross <tgross@hashicorp.com>

Co-authored-by: Bryce Kalow <bkalow@hashicorp.com>

During an upgrade to Nomad 1.4.0, if a server running 1.4.0 becomes the leader
before one of the 1.3.x servers, the old server will crash because the keyring
is initialized and writes a raft entry.

Wait until all members are on a version that supports the keyring before
initializing it.

Post 1.4.0 release

Metrics state is local to the server and needs to use time, which is normally
forbidden in the FSM code. We have a bypass for this rule for
`metrics.MeasureSince` but needed one for `metrics.MeasureSinceWithLabels` as well.

In #14742 we introduced a cached lookup of the `nobody` user, which is only ever
called on Unixish machines. But the initial caching was being done in an `init`
block, which meant it was being run on Windows as well. This prevents the Nomad
agent from starting on Windows.

An alternative fix here would be to have a separate `init` block for Windows and
Unix, but this potentially masks incorrect behavior if we accidentally added a
call to the `Nobody()` method on Windows later. This way we're forced to handle
the error in the caller.

The `hc-install` tool we're using needed a patch for a specific bug, but that's
since been merged. We definitely want to switch to using a standard release from
that project once one is shipped with the CLI, but pinning to HEAD should keep
us for now.

* test: ensure feasible node selected in overlap test

* test: warn when getting close to retry limit

This is probably undocumented for a reason, but the `enabled` toggle in the
`periodic` stanza is very useful so I figured I try adding it to the docs.

The feature has been secretly avaliable since #9142 and was called out in that
PR as being a dubious addition, only added to avoid regressions.

The use case for disabling a periodic job in this way is to prevent it from
running without modifying the schedule. Ideally Nomad would make it more clear
that this was the case, and allow you to force a run of the job, but even with
those rough edges I think users would benefit from knowing about this toggle.

This changeset adds new architecture internals documents to the contributing
guide. These are intentionally here and not on the public-facing website because
the material is not required for operators and includes a lot of diagrams that
we can cheaply maintain with mermaid syntax but would involve art assets to have
up on the main site that would become quickly out of date as code changes happen
and be extremely expensive to maintain. However, these should be suitable to use
as points of conversation with expert end users.

Included:
* A description of Evaluation triggers and expected counts, with examples.
* A description of Evaluation states and implicit states. This is taken from an
  internal document in our team wiki.
* A description of how writing the State Store works. This is taken from a
  diagram I put together a few months ago for internal education purposes.
* A description of Evaluation lifecycle, from registration to running
  All...

Bumps [@hashicorp/platform-cli](https://github.com/hashicorp/web-platform-packages/tree/HEAD/packages/cli) from 2.1.0 to 2.3.0.
- [Release notes](https://github.com/hashicorp/web-platform-packages/releases)
- [Changelog](https://github.com/hashicorp/web-platform-packages/blob/main/packages/cli/CHANGELOG.md)
- [Commits](https://github.com/hashicorp/web-platform-packages/commits/@hashicorp/platform-cli@2.3.0/packages/cli

)

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Previously, the splay timeout was only applied if a template re-render
caused a restart or a signal action. The `change_mode = "script"` was
running after the `if restart || len(signals) != 0` check, so it was
invoked at all times.

This change refactors the logic so it's easier to notice that new
`change_mode` options should start only after `splay` is applied.

This reverts PR #12416 and commit 6668ce02.

While the driver options are well and truly deprecated, this documentation also
covers features like `fingerprint.denylist` that are not available any other
way. Let's revert this until #12420 is ready.

[ui] Bugfix: reinstate the "this variable will be accessible by $job/$group/$task" notification (#14741)

* When we isolated the variable form path to within its component for isolation reasons, we lost the model-level checks for related entites at type-time

* Be a little more functionally pure

* Use Ember.set to appease mirage