Check for changes to affinity, constraints and spread during update

Fixes documentation inaccuracy for spread stanza placement. Spreads can
only exist on the top level job struct or within a group.

comment about nil assumption

Adds checks for affinity and constraint changes when determining if we
should update inplace.

refactor to check all levels at once

check for spread changes when checking inplace update

* client: improve group service stanza interpolation and check_restart support

Interpolation can now be done on group service stanzas. Note that some task runtime specific information
that was previously available when the service was registered poststart of a task is no longer available.

The check_restart stanza for checks defined on group services will now properly restart the allocation upon
check failures if configured.

api: add `StartedAt` in `Node.DrainStrategy`

Update redirects.txt

Nomad monitor - target remote servers

handle the case where we request a server-id which is this current server

update docs, error on node and server id params

more accurate names for tests

use shared no leader err, formatting

rm bad comment

remove redundant variable

Allows user to pass in node-id=leader to forward monitor request to
remote a remote leader.

updates consul template deps to v0.22.1

pin to v0.22.1

nomad: fix dropped test error

test rootfallthrough handler

[docs] Fix link; discuss meta; lint fixes

* remove unused MockPeriodicJob() from tests
* remove unused getIndex() from tests
* remove unused checkIndex() from tests
* remove unused assertIndex() from tests
* remove unused Agent.findLoopbackDevice()

vault: allow overriding implicit vault constraint

There's a bug in version parsing that breaks this constraint when using
a prerelease enterprise version of Vault (eg 1.3.0-beta1+ent). While
this does not fix the underlying bug it does provide a workaround for
future issues related to the implicit constraint. Like the implicit
Connect constraint: *all* implicit constraints should be overridable to
allow users to workaround bugs or other factors should the need arise.

remove accidental project leakage in api/ package

vault: check token_explicit_max_ttl as well

Vault 1.2.0 deprecated `explicit_max_ttl` in favor of
`token_explicit_max_ttl`.

closes #6672