* Upgrade to using hashicorp/go-metrics@v0.5.4
This also requires bumping the dependencies for:
* memberlist
* serf
* raft
* raft-boltdb
* (and indirectly hashicorp/mdns due to the memberlist or serf update)
Unlike some other HashiCorp products, Nomads root module is currently expected to be consumed by others. This means that it needs to be treated more like our libraries and upgrade to hashicorp/go-metrics by utilizing its compat packages. This allows those importing the root module to control the metrics module used via build tags.
Their release notes are here: https://github.com/golang-jwt/jwt/releases
Seemed wise to upgrade before we do even more with JWTs. For example
this upgrade *would* have mattered if we already implemented common JWT
claims such as expiration. Since we didn't rely on any claim
verification this upgrade is a noop...
...except for 1 test that called `Claims.Valid()`! Removing that
assertion *seems* scary, but it didn't actually do anything because we
didn't implement any of the standard claims it validated:
https://github.com/golang-jwt/jwt/blob/v4.5.0/map_claims.go#L120-L151
So functionally this major upgrade is a noop.
