This upgrade fixes a problem that caused a single listener to monopolize
a Unicorn worker. By default, GitLab Omnibus configures Unicorn to
listen both on a UNIX domain socket and a TCP socket. One of those
sockets can be starved if many requests are queued
(https://yhbt.net/unicorn-public/20200416092457.GA5000@dcvr/).

Full list of changes:
https://github.com/defunkt/unicorn/compare/v5.4.1...v5.5.5

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/213257

Merge branch '18140-add-to-next-and-previous-commit-buttons-when-viewing-commits-in-merge-request' into 'master'

Add backstage code that allows Diffs app to dynamically respond to changes to `state` `commit`

See merge request gitlab-org/gitlab!29830

Convert request specs to unit for EE::PostReceiveService

See merge request gitlab-org/gitlab!30038

Mark ProcessCommitWorker as idempotent

See merge request gitlab-org/gitlab!30419

Consolidate styles for Design Management

See merge request gitlab-org/gitlab!29558

Docs: Update code owners for dev guidelines

See merge request gitlab-org/gitlab!30372

Add pipeline creation duration histogram metric

Closes #214784

See merge request gitlab-org/gitlab!30025

Sort DS analysers according to scanner id

See merge request gitlab-org/gitlab!30190

Update License Management major version

See merge request gitlab-org/gitlab!30341

Enable compile-once and compile-with-DLL options for dev-server process

Closes #34096

See merge request gitlab-org/gitlab!25149

Migrate deploy_keys to Jest

Closes #194227

See merge request gitlab-org/gitlab!30145

https://gitlab.com/gitlab-org/gitlab/-/merge_requests/30145

Better Geo Out of Date Errors

Closes #211862

See merge request gitlab-org/gitlab!29800

Move more helm command tests to shared examples

Closes #39460

See merge request gitlab-org/gitlab!21863

A large amount of the helm command behavior is shared behavior inherited
from BaseCommand, yet much of the test code was duplicated. This
extracts the common test code into shared examples.

Resolves https://gitlab.com/gitlab-org/gitlab/issues/39460

Ensures all design management sass is
not scattered across multiple files

Fix header name for keyset pagination

See merge request gitlab-org/gitlab!30093

Fix broken link in logging.md

See merge request gitlab-org/gitlab!30440

Remove update function logic from issue.js

See merge request gitlab-org/gitlab!21414

https://gitlab.com/gitlab-org/gitlab/-/merge_requests/21414

Update offline scanning documentation

See merge request gitlab-org/gitlab!30227

Revert "Merge branch 'restrict-user-autocompletes' into 'master'"

See merge request gitlab-org/gitlab!30512

The ProcessCommitWorker processed 1 million "duplicate"
jobs the past 7 days, and spent 120 hours on that.

Duplicate jobs are jobs that get scheduled when there
is already a job in the queue for the same worker with
the same arguments.

If the job was (marked as) idempotent,
we would be able to deduplicate those jobs automatically
when they get scheduled.

Fix second 500 error with NULL restricted visibility levels

Closes #215638

See merge request gitlab-org/gitlab!30414

Handle empty terraform plan

See merge request gitlab-org/gitlab!30002

Add scheduled_at field to jira_imports table

Closes #213808

See merge request gitlab-org/gitlab!30284

Remove duplicate db query in dashboard snippets

See merge request gitlab-org/gitlab!30277

Fix filename & Rails version in Geo framework doc

See merge request gitlab-org/gitlab!30360

Geo: Add PackageFileRegistryFinder to prepare for GraphQL API work

See merge request gitlab-org/gitlab!30137

Resolve "Allow multiple screenshots to be uploaded in copy paste"

See merge request gitlab-org/gitlab!30152

Migrate pipelines_spec.js to Jest

See merge request gitlab-org/gitlab!30232

Re-implement nodemon as a required module so that we can
remove the superfluous config file.

Upgrade Grape v1.1.0 to v1.3.2

Closes #195960

See merge request gitlab-org/gitlab!27276

Add mutation to update limit metric settings on board lists

See merge request gitlab-org/gitlab!29897

Add JSON wrapper cop

See merge request gitlab-org/gitlab!29705

User can enable alert management

See merge request gitlab-org/gitlab!30024