release-23.1: cluster-ui: skip undefined regions on database pages

[THardy98]

Backport 1/1 commits from #106778.

/cc @cockroachdb/release

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Epic: None
Addresses: #106697

This patch skips undefined regions on the databases pages. The undefined behaviour occurs when we try to match a database's node IDs (i.e. the nodes with ranges that contain data belong to one of the database's tables) from the database details endpoint, to nodes' region information from the nodes endpoint.

The nodes endpoint is authoritative and is refreshed at a regular interval. However, the database details endpoint is only fetched once on page load, and it's node information comes from a cache, leading to the potential of stale data (this information is authoritative in 23.1, but not in 22.2).

Consequently when trying to match cached node IDs with recent node regions information, we can come across behaviour where we try to get region information for a node ID that is no longer valid (i.e. in the case of a decommissioned node), resulting in undefined and surfacing outdated node information.

This change ensures that when we encounter such occurrences, we avoid displaying them in the console.

Release note (bug fix): Avoid displaying undefined regions on the databases pages.

Release justification: low risk, UI improvement

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Patches should only be created for serious issues or test-only changes.
• Patches should not break backwards-compatibility.
• Patches should change as little code as possible.
• Patches should not change on-disk formats or node communication protocols.
• Patches should not add new functionality.
• Patches must not add, edit, or otherwise modify cluster versions; or add version gates.

If some of the basic criteria cannot be satisfied, ensure that the exceptional criteria are satisfied within.

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
• The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting).
• New code is protected by a conditional check that is trivial to verify and ensures that it only runs for opt-in clusters.
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.

Add a brief release justification to the body of your PR to justify this backport.

Some other things to consider:

• What did we do to ensure that a user that doesn’t know & care about this backport, has no idea that it happened?
• Will this work in a cluster of mixed patch versions? Did we test that?
• If a user upgrades a patch version, uses this feature, and then downgrades, what happens?

[cockroach-teamcity]

This change is 

[maryliag]

Reviewable status: complete! 1 of 0 LGTMs obtained