dbconsole: improve mixed-version state reporting

In [1], we added an alert to warn the user that a potentially long-running upgrade has not yet been finalized. However, this alert shows up only inside the `Overview` (panel) view. Furthermore, the user may inadvertently close the alert; subsequently, there is no other notification that the upgrade either has been finalized or continues to be running.

Meanwhile, the page header displays the cluster id and the _binary_ version without explicitly indicating that. The latter can be a source of confusion when the cluster remains in a mixed-version state. An average user may interpret the version `23.1.9` (see screenshot below) to mean that the cluster is on that version, especially when the alert isn't visible. Considering that the header (banner) has a lot of unused real-estate, there is an opportunity to make the version information more precise; e.g., it could say `23.1.9 (binary) -- upgrade not finalized`.

E.g., alert shows up only under `Overview` and not `Metrics`,

[1] https://github.com/cockroachdb/cockroach/pull/104688

Jira issue: CRDB-31377

Start in the dbconsole Overview and Metrics views and inspect how the mixed-version alert and page-header version are assembled. Done means the mixed-version status remains visible across these views and the header clearly labels the binary version and whether the upgrade is finalized.

Written by the indexing model from the issue text.