db-console: Insights page makes separate requests for every contention event

When the db-console page gets high contention insights, it makes a separate request to `addStmtContentionInfoApi` for each event. This API is extremely expensive because it's querying `crdb_internal.transaction_contention_events` which results in a cluster-wide fan out.

At the very least, db-console should make a sql request for multiple `waiting_stmt_id` at once, instead of one at a time.

https://github.com/cockroachdb/cockroach/blob/d5f328ea6f3efd8fbe631c97d59f7b74307d22f9/pkg/ui/workspaces/cluster-ui/src/api/stmtInsightsApi.ts#L172

Jira issue: CRDB-44019

Start with pkg/ui/workspaces/cluster-ui/src/api/stmtInsightsApi.ts around the addStmtContentionInfoApi call and trace how high-contention insights are loaded. Check the related request and SQL handling to determine where multiple waiting_stmt_id values can be accepted. Done means the Insights page uses one request for multiple contention events instead of one expensive cluster-wide query per event.

Written by the indexing model from the issue text.