core: swap bolt impl and enable configuring raft freelist sync behavior

If a plugin job fails before successfully fingerprinting the plugins,
the plugin will not exist when we try to delete the job. Tolerate
missing plugins.

This PR modifies the server and client agents to use `go.etc.io/bbolt` as the
implementation for their state stores.

This PR swaps the underlying BoltDB implementation from boltdb/bolt
to go.etc.io/bbolt.

In addition, the Server has a new configuration option for disabling
NoFreelistSync on the underlying database.

Freelist option: https://github.com/etcd-io/bbolt/blob/master/db.go#L81
Consul equivelent PR: https://github.com/hashicorp/consul/pull/11720

The dynamic plugin registry assumes that plugins are singletons, which
matches the behavior of other Nomad plugins. But because dynamic
plugins like CSI are implemented by allocations, we need to handle the
possibility of multiple allocations for a given plugin type + ID, as
well as behaviors around interleaved allocation starts and stops.

Update the data structure for the dynamic registry so that more recent
allocations take over as the instance manager singleton, but we still
preserve the previous running allocations so that restores work
without racing.

Multiple allocations can run on a client for the same plugin, even if
only during updates. Provide each plugin task a unique path for the
control socket so that the tasks don't interfere with each other.

Detection of the full set of plugin capabilities was added in Nomad
1.1 for the volume creation workflow, but these were not added to the
API response for plugins.

* rename method checking that free write claims are available
* use package-level variables for claim errors
* semgrep fix for testify

The volumewatcher test incorrectly represents the change in attachment
and access modes introduced in Nomad 1.1.0 to support volume
creation. This leads to a test that happens to pass but only
accidentally.

Update the test to correctly represent the volume modes set by the
existing claims on the test volumes.

Adding link to interview form

In PR #11892 we updated the `csi_hook` to unmount the volume locally
via the CSI node RPCs before releasing the claim from the server. The
timer for this hook was initialized with the retry time, forcing us to
wait 1s before making the first unmount RPC calls.

Use the new helper for timers to ensure we clean up the timer nicely.

core: remove all traces of unused protocol version

Nomad inherited protocol version numbering configuration from Consul and
Serf, but unlike those projects Nomad has never used it. Nomad's
`protocol_version` has always been `1`.

While the code is effectively unused and therefore poses no runtime
risks to leave, I felt like removing it was best because:

1. Nomad's RPC subsystem has been able to evolve extensively without
   needing to increment the version number.
2. Nomad's HTTP API has evolved extensively without increment
   `API{Major,Minor}Version`. If we want to version the HTTP API in the
   future, I doubt this is the mechanism we would choose.
3. The presence of the `server.protocol_version` configuration
   parameter is confusing since `server.raft_protocol` *is* an important
   parameter for operators to consider. Even more confusing is that
   there is a distinct Serf protocol version which is included in `nomad
   server members` output under the heading `Protocol`. `raft_protocol`
   is the *only* protocol version relevant to Nomad developers and
   operators. The other protocol versions are either deadcode or have
   never changed (Serf).
4. If we were to need to version the RPC, HTTP API, or Serf protocols, I
   don't think these configuration parameters and variables are the best
   choice. If we come to that point we should choose a versioning scheme
   based on the use case and modern best practices -- not this 6+ year
   old dead code.

connect: write envoy bootstrap debugging info

connect: bootstrap envoy using -proxy-id

This PR modifies the Consul CLI arguments used to bootstrap envoy for
Connect sidecars to make use of '-proxy-id' instead of '-sidecar-for'.

Nomad registers the sidecar service, so we know what ID it has. The
'-sidecar-for' was intended for use when you only know the name of the
service for which the sidecar is being created.

The improvement here is that using '-proxy-id' does not require an underlying
request for listing Consul services. This will make make the interaction
between Nomad and Consul more efficient.

Closes #10452

When Consul Connect just works, it's wonderful. When it doesn't work it
can be exceeding difficult to debug: operators have to check task
events, Nomad logs, Consul logs, Consul APIs, and even then critical
information is missing.

Using Consul to generate a bootstrap config for Envoy is notoriously
difficult. Nomad doesn't even log stderr, so operators are left trying
to piece together what went wrong.

This patch attempts to provide *maximal* context which unfortunately
includes secrets. **Secrets are always restricted to the secrets/
directory.** This makes debugging a little harder, but allows operators
to know exactly what operation Nomad was trying to perform.

What's added:

- stderr is sent to alloc/logs/envoy_bootstrap.stderr.0
- the CLI is written to secrets/.envoy_bootstrap.cmd
- the environment is written to secrets/.envoy_bootstrap.env as JSON

Accessing this information is unfortunately awkward:
```
nomad alloc exec -task connect-proxy-count-countdash b36a cat secrets/.envoy_bootstrap.env
nomad alloc exec -task connect-proxy-count-countdash b36a cat secrets/.envoy_bootstrap.cmd
nomad alloc fs b36a alloc/logs/envoy_bootstrap.stderr.0
```

The above assumes an alloc id that starts with `b36a` and a Connect
sidecar proxy for a service named `count-countdash`.

If the alloc is unable to start successfully, the debugging files are
only accessible from the host filesystem.

deps: upgrade hashicorp/raft to v1.3.5

build: BIN value must use single-path GOPATH value

namespace refactoring

When GOBIN is not set, BIN must be set to the single-path workaround
value of GOPATH, because Circle.