Drop scheduling logic from the metadata indexers.
Remove OriginHeadIndexer.next_step. Remove OriginIntrinsicMetadataIndexer. Renames FullOriginIntrinsicMetadataIndexer to OriginIntrinsicMetadataIndexer.
Depends on !99 (closed)
Test Plan
tox + docker
Migrated from D987 (view on Phabricator)