The background migration MigrateMergeRequestDiffCommitUsers processes
batches of merge_request_diff_commits rows in batches. These migrations
have been running for several weeks now.

Unfortunately, on GitLab.com we are running into problems with the
remaining 750 or so jobs. Some jobs take a few minutes to complete,
while others can take over an hour to complete. The scheduling interval
was originally just a few minutes. This lead to many jobs being thrown
away, as they could not be picked up fast enough when there is a long
running job. Rescheduling jobs with a greater interval hasn't proven
successful.

In this commit we add a new background migration to clean up the pending
work. This background migration picks up a single job (in reverse
order), processes it, then schedules the next job. This approach
prevents jobs from conflicting with each other if they take too long.

In addition, we change the existing migration to not process jobs that
have already been processed. This way existing jobs that have yet to be
picked up won't lead to duplicate work.

Both the old and new migration _can_ process work in parallel, as they
are different background migration classes. This shouldn't pose any
problems. For the last few weeks we've been manually running jobs in a
Rails console in parallel to the Sidekiq jobs, without any problems
surfacing.

See https://gitlab.com/gitlab-org/gitlab/-/issues/334394 for more
information.

Changelog: added

Resolve "Expand the content of the top level Infra page"

See merge request gitlab-org/gitlab!67671

Pipeline Security: Rename "scanner" to "tool"

See merge request gitlab-org/gitlab!68713

Remove DAST site validation feature flags

See merge request gitlab-org/gitlab!68330

E2E: Improve failure messages for large github import spec

See merge request gitlab-org/gitlab!68698

Update Gitaly version

See merge request gitlab-org/gitlab!68744

Reorder vuln check criteria

See merge request gitlab-org/gitlab!68503

GraphQL: Add runners to groups query [RUN AS-IF-FOSS]

See merge request gitlab-org/gitlab!65673

Update policies#new view to pass up updated data

See merge request gitlab-org/gitlab!68317

Add tests for each individual search index

See merge request gitlab-org/gitlab!66986

Enable assumeImmutableResults in DAST Scanner Profiles

See merge request gitlab-org/gitlab!68726

Refactor post-issue-update tasks to be more readable

See merge request gitlab-org/gitlab!64811

Revert "Merge branch 'ph/333351/fixSuggestionsNewLines' into 'master'"

See merge request gitlab-org/gitlab!68717

Stringify policy yaml response in scanExecutionPolicies graphql query

See merge request gitlab-org/gitlab!68656

Refactor sidebar menus link method

See merge request gitlab-org/gitlab!68441

Removes subtransaction in internal id generator

See merge request gitlab-org/gitlab!68617

Enable `assumeImmutableResults` in storage-counter

See merge request gitlab-org/gitlab!68629

Add the retry button to failed migrations

See merge request gitlab-org/gitlab!67504

Add direct group dependency proxy predefined variable

See merge request gitlab-org/gitlab!68661

Add CI_DEPENDENCY_PROXY_DIRECT_GROUP_IMAGE_PREFIX
predefined environment variable to projects.

Changelog: added

Update Gitaly version

See merge request gitlab-org/gitlab!68725

Persist groups configured to use an Agent

See merge request gitlab-org/gitlab!68023

Add default value to vulnerabilities_allowed column

See merge request gitlab-org/gitlab!68501

Making issue and commit links distinctly visible

See merge request gitlab-org/gitlab!68063

https://gitlab.com/gitlab-org/gitlab/-/issues/330455

Coloring only links in the description, not titles

We might still want to highlight cross-references in
other places, but it seems that this is more scoped
to what https://gitlab.com/gitlab-org/gitlab/-/issues/330455
specifies.

Changelog: changed
MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/68063

Set assumeImmutableResults to true in the Apollo provider
for DAST Scanner Profiles, refer
https://gitlab.com/groups/gitlab-org/-/epics/6025

Puts the changes under the use_insert_all_in_internal_id feature flag

This prevents a subtransaction when we insert an InternalId record. We
make use of `insert_all` which ignores unique violations without
aborting the parent transaction.

Most of the sidebar menus default to the first menu item link as the
main menu link.

Instead of writing it in every menu, we can just move it to the
base menu class and let the other menus inherit it. We'd just
need to override those with a different behavior.

This reverts merge request !68532