Prepare indexes for converting notes.id to bigint

What does this MR do and why?

We need these indexes in order to swap notes.id and notes.id_convert_to_bigint. As it takes a lot of time to create them, we have to do it async for GitLab.com.

This is extracted from !119705 (merged).

See #392815 (closed) for more details.

Changelog: other

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