Sync create indexes for ci_stages pipeline_id conversion

What does this MR do and why?

Sync create indexes for ci_stages pipeline_id conversion

This is the second step to synchronously create indexes for ci_stages

See https://docs.gitlab.com/ee/development/database/adding_database_indexes.html#add-a-migration-to-create-the-index-synchronously

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Related to #422813 (closed)