PR #87301 - sql: support ALTER INDEX ... VISIBILITY ...

[cockroach-teamcity]

Related PR: https://github.com/cockroachdb/cockroach/pull/87301 Commit: https://github.com/cockroachdb/cockroach/commit/452a2de1fb99885b74cd590b72c912e76f25f360 Informs: CRDB-16312 CRDB-16312

---

Release note (sql change): ALTER INDEX ... VISIBILITY ... is now supported. It can change an index visibility to any visibility within [0.0, 1.0]. Visibility 0.0 means the index is not visible to the optimizer, while visibility 1.0 means the index is fully visible. A value in the range (0.0, 1.0) means the index will be visibile to the corresponding fraction of queries.

Co-authored-by: Rebecca Taft [email protected]