Rename duplicated migration classes

Leonardo da Rosarequested to merge
419193-prevent-name-clash-between-database-and-search-migrations-follow-up into master

What does this MR do and why?

  1. Rename two database migrations that were clashing with Elasticsearch migrations: BackfillInternalOnNotes and AddInternalToNotes.
  2. Adds a new spec to ensure that no clashing will happen in the future.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #419193 (closed)

Edited by Andy Schoenen

Merge request reports