When updating references in UserMergeBranch failed due to a concurrent
update of the same reference, then Gitaly used to return no error at all
but instead just return an empty gRPC response. This behaviour isn't
obvious at all and easy to get wrong. Furthermore, Rails didn't have any
information about what went wrong.

To fix this, Gitaly has introduced a new error type which is returned in
case there was a race updating the reference. Instead of returning
successful, it now returns an error with a ReferenceUpdateError embedded
inside of it. This allow us to extract this error and thus know exactly
what happened, including the reference that failed to update with both
its old and new expected object ID values.

Update the Gitaly client to handle this error in a backwards-compatible
fashion. For now this means that we silently ignore it like we used to
do with the old error as well.

The UserMergeBranch RPC returns error details on some error conditions
which allow the caller to do more fine-grained error handling. The tests
which exercise this for the AccessCheckError is verifying that this
works by returning an error whose status details metadata is set to an
already-serialized string. This is hard to read and ultimately obscures
what kind of error details we want the server to return.

Convert the test to instead construct the serialized error details from
the protobuf definitions.

We're about to make use of a new error type introduced for the
UserMergeBranch RPC, which requires us to upgrade to v14.8.0-rc1 of the
Gitaly Gem. Update our Gemfile to prepare for this.

Add training item loading in vulnerability details page

See merge request gitlab-org/gitlab!78709

Add mutation for updating user preferences

See merge request gitlab-org/gitlab!79127

Upgrade to Sidekiq 6.4

See merge request gitlab-org/gitlab!79009

Replace deprecated usage of find/findAll in ee/spec/frontend/approvals

See merge request gitlab-org/gitlab!78632

Update runner registration token reset modal

See merge request gitlab-org/gitlab!79136

Add reverse lock order option to FK removal

See merge request gitlab-org/gitlab!78968

Remove import_redis_increment_by feature flag

See merge request gitlab-org/gitlab!79130

Swap FK ci_builds_metadata to projects for LFK

See merge request gitlab-org/gitlab!79039

Added self-managed and a small runner update

See merge request gitlab-org/gitlab!78754

Improve Jira Connect search UX

See merge request gitlab-org/gitlab!78994

Addressing reviewer feedback in
the Jira Connect app search functionality.

Changelog: changed

Add elements to incident page to render escalation info

See merge request gitlab-org/gitlab!78926

Adds elements to html served by backend for frontend to
render incident status and escaltion policy. Includes
exposing permissions.

Moves feature flag check from EE to CE, to ensure the
page does not contain new elements if the feature is
disabled.

Adding Secure Files API

See merge request gitlab-org/gitlab!78227

More spelling errors in docs

See merge request gitlab-org/gitlab!79156

Broken what's new link for "Add personal README to profile"

See merge request gitlab-org/gitlab!79145

Add ability to search iterations by cadence title

See merge request gitlab-org/gitlab!76231

- Update the iterations GraphQL API to support iterations search
using the attributes title or cadence title.

Changelog: added
EE: true

Added function signature to expand diff line

See merge request gitlab-org/gitlab!79028

Replace `owner` with array of owners in project admin show page

See merge request gitlab-org/gitlab!78974

Roadmap setting - Move daterange to sidebar

See merge request gitlab-org/gitlab!79084

Docs spelling errors

See merge request gitlab-org/gitlab!79154

Revert "Revert "Upgrade GitLab Pages to 1.51.0""

See merge request gitlab-org/gitlab!79182

Milestone description: show issuable reference title

See merge request gitlab-org/gitlab!79027

Changelog: fixed

Quarantine broken free_trial_spec.rb

See merge request gitlab-org/gitlab!79174

Add docs for reducing data transfer costs

See merge request gitlab-org/gitlab!78614

Prevent pushing null when creating a new label

See merge request gitlab-org/gitlab!79121

This reverts commit b59278f9.

Clarify in docs trigger keyword

See merge request gitlab-org/gitlab!79162

Update add-on to include transfer

See merge request gitlab-org/gitlab!79091