Makes use of markdownlint for automated cleanup

Because for now, we're changing the format.

Related to: https://gitlab.com/gitlab-org/gitlab-docs/-/issues/1751

Fix indentation of lists and table alignment

Related to: https://gitlab.com/gitlab-org/gitlab/-/issues/433277

Update the links in all docs except user and admin pages

Because the left nav is changing
and will have a button instead
of carat, and no magnifying glass.

Related to: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/127935

Because we changed the way we
do the markdown.

Related to: https://gitlab.com/gitlab-org/gitlab-docs/-/issues/1690

Update validation to support variables in addition to the previous values.
Validation of variables in cache:policy is done by Gitlab Runner at runtime
Update docs

Changelog: added

Thanks to the new TLD, we should wrap all of these names ending in
.zip in backticks so they aren't rendered as links to who-knows-where.

Add a new `fallback_keys` keyword as part of the `cache` configuration.
This will allow users to specify multiple cache keys as a fallback
mechanism if there is no hit for the primary cache key.

Changelog: added

Split job artifacts page into a main topic page
and a separate troubleshooting page. Also, move both
to be nested under ci/jobs rather than ci/pipelines

Part of https://gitlab.com/gitlab-org/gitlab/-/issues/393190

Changelog: changed

[Ruff](https://beta.ruff.rs/) supports [over 500 lint rules](https://beta.ruff.rs/docs/rules) and can be used to replace [Flake8](https://pypi.org/project/flake8/) (plus dozens of plugins), [isort](https://pypi.org/project/isort/), [pydocstyle](https://pypi.org/project/pydocstyle/), [yesqa](https://github.com/asottile/yesqa), [eradicate](https://pypi.org/project/eradicate/), [pyupgrade](https://pypi.org/project/pyupgrade/), and [autoflake](https://pypi.org/project/autoflake/), all while executing (in Rust) tens or hundreds of times faster than any individual tool.

We use `ruff --format=gitlab` to rapidly provide intuitive feedback to contributors.

Runners have 3 types, shared, group, and project. They are based on
where runners were registered. Project runners used to be called
"specific".

This change renames old occurrences of "specific" when referring to
runners, to update them to "project".

Changelog: changed

Related epic: https://gitlab.com/groups/gitlab-com/-/epics/1940

Because the menu changed.
Related to: https://gitlab.com/gitlab-org/gitlab/-/issues/366082/

The option of caching whole .venvs seems attractive, because it represents the
end-result of an installation process and would therefore entail the least
rework between jobs. Unfortunately, venvs cannot be reliably relocated from one
directory to another, and this is what happens implicitly when using caches
across runners.

pypa's virtualenv is explicit about this; venv is not (but relocating still
doesn't work)
https://virtualenv.pypa.io/en/legacy/userguide.html#making-environments-relocatable

> The --relocatable option currently has a number of issues, and is not
> guaranteed to work in all circumstances. It is possible that the option will be
> deprecated in a future version of virtualenv.

Changelog: added
Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/361643

Minor CI-CD caching style updates

Merge branch 'pedropombeiro/330047/use-protected-suffix-for-cache-name' into 'master'

See merge request gitlab-org/security/gitlab!1551

Changelog: security