Merge the gitlab-shell "gitlab-keys" functionality into GitLab CE

Closes #56089

See merge request gitlab-org/gitlab-ce!25598

In this commit, some methods that aren't being used
are removed from `Gitlab::Shell`. They are the ff:
- `#remove_keys_not_found_in_db`
- `#batch_read_key_ids`
- `#list_key_ids`

The corresponding methods in `Gitlab::Keys` have been
removed as well.

Revert "New Repository#insights_config method"

See merge request gitlab-org/gitlab-ce!26315

Add users search results to global search

Closes #25973

See merge request gitlab-org/gitlab-ce!21197

Remove diff tree filtering feature flag

See merge request gitlab-org/gitlab-ce!26273

Make runners token encryption to be optional

See merge request gitlab-org/gitlab-ce!26223

This reverts merge request !26183

Bump Rugged to 0.28.0

See merge request gitlab-org/gitlab-ce!25660

Remove before_script from DAST vendored template

See merge request gitlab-org/gitlab-ce!26281

Link to the gitaly repository's Beginniner's Guide documentation

See merge request gitlab-org/gitlab-ce!25627

Copyedit pipelines-related documentation

Closes #59006

See merge request gitlab-org/gitlab-ce!26198

Refactor new content for stage keyword

See merge request gitlab-org/gitlab-ce!25953

Add registry to dev arch docs

See merge request gitlab-org/gitlab-ce!25951

Add registry to dev arch docs

See merge request gitlab-org/gitlab-ce!25951

This version bump makes things consistent between Gitaly and
fixes a significant number of bugs:
https://github.com/libgit2/libgit2/releases

This also decreases disk space of Omnibus builds by ~30 MB.

There is also a workaround for
https://github.com/libgit2/rugged/issues/785. If Gitaly or another
process changes .gitconfig while Rugged has the file loaded,
Rugged::Repository#each_key will report stale values unless a lookup is
done first.

This bug only manifests in a spec because we are using both Gitaly and
Rugged at the same time there, and we normally don't use Rugged in the
CE/EE code in this way.

Merge branch '47491-gitlab-fakeapplicationsettings-doesn-t-respond-to-all-the-methods-applicationsetting-responds-to-itself' into 'master'

Introduce ApplicationSettingImplementation

Closes #47491

See merge request gitlab-org/gitlab-ce!25803

Add artillery.io load testing script and rake tasks

See merge request gitlab-org/gitlab-ce!26210

Also add rake tasks that makes use of existing performance data
genertion task.

So the fake can enjoy it, too. We don't use `prepend`
because that'll require we change `allow_any_instance_of` to
`expect_next_instance_of`, but that's not very easy to do.
We can do that later.

Fix undefined variable error on json project views

See merge request gitlab-org/gitlab-ce!26297

This mistake seems to have always been there, but it only resulted in
errors on the `/explore*.json` since they were the one that _actually_
relied on the local variables.

Fix spec for routes to the GraphqlController

See merge request gitlab-org/gitlab-ce!26231

Implement suggestion diff lines parser

See merge request gitlab-org/gitlab-ce!26069

Fix test-plan label in the template

See merge request gitlab-org/gitlab-ce!26283

Fixed backup of non default upload directory

See merge request gitlab-org/gitlab-ce!25736

Replaced Settings with Gitlab.config for uniformity

Updating nginx_status link in index.md to use the proper anchor to nginx.html

See merge request gitlab-org/gitlab-ce!26245

Use the same standard for method names on project activity and menu page objects

See merge request gitlab-org/gitlab-ce!24738

... page objects.

Also, update the affected test case.

I choose `click_...` instead of `go_to_...` since it describes
better what the method really does, which is clicking on something.

I know there are other places in the code where methods start with
`click_` and others where methods start with `go_to_`, with that
I'd like to start a discussion or be pointed to the right issue if
there is already one so that we can address this in the whole
framework.
This contribution could be the start in the direction of using the
standard chosen here.

Move EE specific code out of lib/gitlab

See merge request gitlab-org/gitlab-ce!25741

Removes EE differences for clusters/_sidebar.html.haml

Closes gitlab-ee#10428

See merge request gitlab-org/gitlab-ce!26271