ui: introduce schema insights page on db-console

[cockroach-teamcity]

Exalate commented:

Related PR: cockroachdb/cockroach#86317
Commit: cockroachdb/cockroach@2be29c6

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Release note (ui change): Added new Schema Insights page to DB Console.
The Schema Insights page displays a table of schema insights - currently
different types of index recommendations (i.e. drop/create/replace index
recommendations). Each schema insight row offers the user the ability to
execute the corresponding SQL query that realizes their schema insight
via a clickable button. Filters are available to filter the surfaced
schema insights by database and insight type, as well as search.

Release justification: low risk, high benefit changes to existing
functionality

Jira Issue: DOC-5480