Backfill existing workspaces with PATs

What does this MR do and why?

Draft: Backfill existing workspaces with PATs

Related to #423006 (closed)

Migration output

 bin/rails db:migrate:up:main VERSION=20230909120000 RAILS_ENV=development
main: == [advisory_lock_connection] object_id: 226720, pg_backend_pid: 2760914
main: == 20230909120000 QueueBackfillWorkspacePersonalAccessToken: migrating ========
main: == 20230909120000 QueueBackfillWorkspacePersonalAccessToken: migrated (0.0494s) 
main: == [advisory_lock_connection] object_id: 226720, pg_backend_pid: 2760914

$ bin/rails db:migrate:down:main VERSION=20230909120000 RAILS_ENV=development
main: == [advisory_lock_connection] object_id: 226780, pg_backend_pid: 2761250
main: == 20230909120000 QueueBackfillWorkspacePersonalAccessToken: reverting ========
main: == 20230909120000 QueueBackfillWorkspacePersonalAccessToken: reverted (0.0155s) 

main: == [advisory_lock_connection] object_id: 226780, pg_backend_pid: 2761250

Query plans

We create each personal access token and update each workspace individually. We expect < 250 records on Gitlabdotcom and less on self managed.

How to set up and validate locally

See the spec to run the migrations

MR acceptance checklist

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

• I have evaluated the MR acceptance checklist for this MR.