* ui: show region in header gutter when only one region exists
This PR adds a plain text label of the region to the header when there is
only one region present. Before, nothing was showin in this case, and a
dropdown was shown on federated clusters.
The use case here is for operators of multiple non-federated Nomad clusters,
when all the UI's involved otherwise look identical.
* [ui] Signing in with a token explicitly sets the region dropdown activeRegion (#24347)
* Signing in with a token explicitly sets the region dropdown activeREgion
* Test and Select a Region default text
* Account for 403 on mocked agent members req
* Dont show the region if it isnt set in agent config
* Small padding css change
* unit test condition moved to stubbable acceptance test
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Co-authored-by: Phil Renaud <phil.renaud@hashicorp.com>
