Add structs and fields to support the Nomad Pools Governance Enterprise
feature of controlling node pool access via namespaces.
Nomad Enterprise allows users to specify a default node pool to be used
by jobs that don't specify one. In order to accomplish this, it's
necessary to distinguish between a job that explicitly uses the
`default` node pool and one that did not specify any.
If the `default` node pool is set during job canonicalization it's
impossible to do this, so this commit allows a job to have an empty node
pool value during registration but sets to `default` at the admission
controller mutator.
In order to guarantee state consistency the state store validates that
the job node pool is set and exists before inserting it.
Fixes#14617
Dynamic Node Metadata allows Nomad users, and their jobs, to update Node metadata through an API. Currently Node metadata is only reloaded when a Client agent is restarted.
Includes new UI for editing metadata as well.
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Co-authored-by: Phil Renaud <phil.renaud@hashicorp.com>
