Documentation for delayed jobs

Closes #52127

See merge request gitlab-org/gitlab-ce!22117

Add Filesystem Performance Benchmarking documentation

See merge request gitlab-org/gitlab-ce!22202

Revert GitLab Pages version to v1.1.0

See merge request gitlab-org/gitlab-ce!22277

This works around the problem with domains not working
due to https://gitlab.com/gitlab-org/gitlab-pages/issues/170.

Filesystem performance can have a big impact on overall GitLab
performance, especially for actions that read or write Git
repositories. This information will help benchmark filesystem
performance against known good and bad real-world systems.

Prettify all the things (part 5)

See merge request gitlab-org/gitlab-ce!22255

Prettify all the things (part 2)

See merge request gitlab-org/gitlab-ce!22250

Merge branch '52103-dropzone-css-is-failing-to-load-on-rspec-dev-and-staging-11-4-0-rc' into 'master'

Resolve "Dropzone css is failing to load on rspec, dev and staging 11.4.0 RC"

Closes #52103

See merge request gitlab-org/gitlab-ce!22272

Convert remaining issue board components into ES module syntax

See merge request gitlab-org/gitlab-ce!22210

QA: Retry registration before failing

See merge request gitlab-org/gitlab-ce!22033

[QA] Fix a wrong constant name

Closes gitlab-org/quality/nightly#22

See merge request gitlab-org/gitlab-ce!22264

Add allowance to merge feature flags MRs

See merge request gitlab-org/gitlab-ce!22267

Add `TOP_UPSTREAM_SOURCE_SHA` in `scripts/trigger-build`

See merge request gitlab-org/gitlab-ce!22260

Enhance and test JSON schema for deployments

See merge request gitlab-org/gitlab-ce!22266

Registration intermittently fails without an obvious cause.
The action to click the button seems to move focus to the right button
but nothing happens.
This change attempts to retry the action under the assumption that
Capybara or Chrome is misbehaving.
It also updates the selectors for the sign up page.

Fix broken link and file improvements

See merge request gitlab-org/gitlab-ce!22244

After the 7th it is OK to merge code changes that are merged as long it
is behind a feature flag.