Uninstall cluster applications (backend services)

Closes #60665

See merge request gitlab-org/gitlab-ce!27096

These builder methods are using user provided input inside a public_send
but this is safe to do in this instance because before they are called
we check before calling them that they match an expected application
name.

In order to not miss any errors since we are not checking the return
value of update

Basically does the reverse of after_transition to :installed.

Add endpoint to delete/uninstall a cluster application

Add specs

Only prometheus can be uninstalled atm, the rest will be dealt with
later.

Presumption is that new application types will have uninstallation
implmemented at the same time.

Rescue and put into :uninstall_errored if something goes wrong while
destroying, which can happen. I think it is safe to expose the full
error message from the destroy error.

Remove the :uninstalled state as no longer used.

+ to monitor progress of uninstallation pod

Added :uninstalled state as wasn't sure if we should be destroying the
cluster apps

Fix pipelines for merge requests does not show pipeline page when source branch   is removed

Closes #60432

See merge request gitlab-org/gitlab-ce!27803

Source branch can be removed after the merge and
we have to make sure to avoid rendering links if it's the case.

Regenerate gitlab.pot file

See merge request gitlab-org/gitlab-ee!11933

Docs: Add intro and reorg CI index

Closes #58323

See merge request gitlab-org/gitlab-ce!27620

Plus: add note for .com users

Merge branch '60476-actionview-missingtemplate-missing-template-projects-issues-_merge_requests-with-locale-en-formats-html-varian' into 'master'

Delete leftover code for referenced_merge_requests endpoint

Closes #60476

See merge request gitlab-org/gitlab-ce!27335

Propagate ENV vars to SAST and Dependency Scanning Docker containers only if they are set

See merge request gitlab-org/gitlab-ee!11523

This reverts commit 0c4a25f3, reversing
changes made to 6513028e.

This reverts commit cfed90dc, reversing
changes made to a1e84c1a.

Explicityly require `gl_repository` in internal api spec.

Closes #11387

See merge request gitlab-org/gitlab-ee!11900

Explicitly requiring `Gitlab::GlRepository` in the spec that requires
it makes sure it is correctly prepended with
`EE::Gitlab::Repository`.

Otherwise, if a spec before it autoloaded one of the constants from
within `Gitlab::GlRepository` the module would not be prepended.

Fixed boards card dragging styling

Closes #61050

See merge request gitlab-org/gitlab-ce!27802

Extract EE specific files/lines for Discussion spec/requests/api

Closes #6670

See merge request gitlab-org/gitlab-ee!10603