Move commit documents to new index

Add an Advanced Search migration that pauses indexing, creates the new index (with commit mappings), moves the commit documents over to the new index.

Update the GITLAB_ELASTICSEARCH_INDEXER to use the tag created in gitlab-elasticsearch-indexer#87 (closed). Ensure reads and writes for commit use the new index once the migration is completed.

Note: Number of Elasticsearch shards can be configured per index. Determine optimal settings for the number of shards for thew new index.

Add a the index to the existing index tests https://gitlab.com/gitlab-org/gitlab/-/tree/master/qa/qa/specs/features/ee/api/enablement/elasticsearch/index_tests