BBM: Recalculate 2FA for minimal_access_users

Related to #534094 (closed) & !225038 (merged)

What does this MR do and why?

• Recalculate group-level 2FA enforcement for ~4450 users with a minimal_access_role
• Occurs as a post-deploy migration

Database Review

Introduced !225317 (b20ced8c) in the first commit which was later optimized after reviews in !235857 (closed) to the current iteration.

db:check-migrations

https://gitlab.com/gitlab-org/gitlab/-/jobs/14795939540

Partial index

exec CREATE INDEX tmp_idx_members_on_access_level_source_type_requested_at_id ON members USING btree (id) WHERE ((access_level = 5) AND (source_type = 'Namespace') AND (requested_at IS NULL));

Time Estimation

Based on !235857 (comment 3391823398), it should take ~11hrs not 3 months like the bot's estimate.

Post Deployment Tracking

Steps

1. Verify deployment with chatops: /chatops gitlab run batched_background_migrations list --job-class-name RecalculateMinAccessTwoFactorEnforcementOnMembers
2. Use kibana with json.message: Minimal_access user group 2FA enforcement changed. using the pubsub-sidekiq-inf-gprd* data-view to visualize progress: https://log.gprd.gitlab.net/app/r/s/4Od5F
3. If some goes wrong, pause/resume: /chatops gitlab run batched_background_migrations pause MIGRATION_ID
4. Leave a confidential note update on the main work item at the beginning and end.

MR acceptance checklist

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