Remove use_model_load_balancing feature flag and GITLAB_USE_MODEL_LOAD_BALANCING env var

See merge request gitlab-org/gitlab!83162

Use gl-form-radio for setting primary security training provider

See merge request gitlab-org/gitlab!83563

Previously these feature flags and environment variables were introduced
as a way to control the rollout of a new CI database. The new CI
database needs to be configured in `config/database.yml` but since
changing this required a full redeployment of all hosts it was not going
to be as easy to switch on/off as a feature flag so this feature flag
was setup such that we just ignored the values in `config/database.yml`
unless the feature flag was set.

Now that we've deployed "Phase 3" in production
https://gitlab.com/gitlab-com/gl-infra/production/-/issues/6513 we no
longer need these feature flags or environment variables to enable this
behaviour. Now we just use the values as set in the
`config/database.yml`.

Changelog: other

Link to the list of supported Markups

See merge request gitlab-org/gitlab!83247

Revert "Merge branch 351853-vsa-add-empty-state-at-the-group-level-when-there-are-no-custom-value-streams"

See merge request gitlab-org/gitlab!83706

Rename read policy for security orchestration policies

See merge request gitlab-org/gitlab!83649

Change default search rate limits

See merge request gitlab-org/gitlab!83474

Changelog: changed

Use neutral colours for nav background

See merge request gitlab-org/gitlab!83593

Revert "Merge branch '351853-vsa-add-empty-state-at-the-group-level-when-there-are-no-custom-value-streams' into 'master'"

This reverts commit edf916c8, reversing
changes made to 823defaa.

Update Docs To Add When Token Attribute Was Added

See merge request gitlab-org/gitlab!77981

Update Artifacts docs for artifact expiry removal

See merge request gitlab-org/gitlab!83372

Add OID filter example to LDAP troubleshooting doc

See merge request gitlab-org/gitlab!83669

Add a note about data volume consideration

See merge request gitlab-org/gitlab!83461

Add rule for quarantining nightly e2e tests

See merge request gitlab-org/gitlab!83463

Update doc/user/project/repository/mirror/index.md

See merge request gitlab-org/gitlab!80706

Registry import enqueuer uses migration_plan

See merge request gitlab-org/gitlab!83365

Schedule async index build for ci_job_artifacts

See merge request gitlab-org/gitlab!83664

Implement ArkoseLabs sign-in challenge

See merge request gitlab-org/gitlab!82737

Our purpose-built index for removal of expired records from
ci_job_artifacts does not exclude artifacts where expire_at is null.
This means job traces, which get unlocked but have no expiration, are
polluting an index that would otherwise be a clean ready-for-removal
queue and much smaller.

Changelog: performance

Rename scheduled jobs for master and nightly

Update the ready_for_import scope on ContainerRepository
to use the new migration_plan column to reduce the
number of JOINs in the query.

Adds an index on migration_plan.

EE: true
Changelog: performance