Add new Elastic commit indexer worker

Description

This adds the new Search::Elastic::CommitIndexerWorker to replace ElasticCommitIndexerWorker because the wiki parameter is no longer needed. The new worker and its spec are the same as the previous worker, I only adjusted some calls without the wiki parameter.

I'm adding a feature flag rename_commit_indexer_worker to enable the new worker when the Sidekiq deployment finishes.

Reference: https://docs.gitlab.com/development/sidekiq/compatibility_across_updates/#renaming-worker-classes

Related to #518703 (closed).