Automatic reindexing can block vacuum progress

In gitlab-com/gl-infra/production#7852 (comment 1130123525), a weekend reindexing operation took a lock on ci_builds that blocked wraparound-prevention autovacuum on gitlab.com while reindexing index_ci_builds_on_project_id_and_name_and_ref for over 18 hours. This led to significant dead tuple accumulation and degraded query performance.

We should change the reindexing process so that it either avoids or recovers from this scenario.