Our friends at GitHub show the programming languages for a long time,
and inspired by that this commit means to create about the same
functionality.

Language detection is done through Linguist, as before, where the
difference is that we cache the result in the database. Also, Gitaly can
incrementaly scan a repository. This is done through a shell out, which
creates overhead of about 3s each run. For now this won't be improved.

Scans are triggered by pushed to the default branch, usually `master`.
However, one exception to this rule the charts page. If we're requesting
this expensive data anyway, we just cache it in the database.

Edge cases where there is no repository, or its empty are caught in the
Repository model. This makes use of Redis caching, which is probably
already loaded.

The added model is called RepositoryLanguage, which will make it harder
if/when GitLab supports multiple repositories per project. However, for
now I think this shouldn't be a concern. Also, Language could be
confused with the i18n languages and felt like the current name was
suiteable too.

Design of the Project#Show page is done with help from @dimitrieh. This
change is not visible to the end user unless detections are done.

The status is shown for
- The author of a commit when viewing a commit
- Notes on a commit (regular/diff)
- The user that triggered a pipeline when viewing a pipeline
- The author of a merge request when viewing a merge request
- The author of notes on a merge request (regular/diff)
- The author of an issue when viewing an issue
- The author of notes on an issue
- The author of a snippet when viewing a snippet
- The author of notes on a snippet
- A user's profile page
- The list of members of a group/user

This can be done trough the API for the current user, or on the
profile page.

- dont remove todos for authos & assignees
- remove todos for project guests

This adds a database migration that creates routes for any projects and
namespaces that don't already have one. We also remove the runtime code
for dynamically creating routes, as this is no longer necessary.

Backports relevant changes made in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/5163 to CE

Partially addresses #47424.

Partially addresses #47424.

For directories application_settings --> labels.

Partially addresses #47424.

Partially addresses #47424.

This makes it more explicit that an environment is not a stop action,
but instead is merely contains a stop action.

This reverts commit 4d9a3f42, reversing
changes made to ecf9c145.

It allows user to automatically import multiple repositories
with nested structure by uploading a manifest xml file.

AOSP project was used as an example during development of this feature.

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Refactor AutocompleteSources#label:

1. The return value was inconsistent, sometimes returning a hash and sometimes returning an ActiveModel.
2. It was inconsistent with respect to other methods in the class since they all return ActiveModels.