Adds sorting to deployments API through the `order_by` and sort
`fields`.

See https://github.com/rails/rails/pull/24658#issuecomment-212651965

Enables project milestone deletion via DELETE /projects/:id/milestones/:milestone_id

We should use this limit everywhere, but especially in project search results,
where we could be highlighting very long single lines. (Typical examples:
minified JavaScript, and JSON data files.)

A file containing /:\d+:/ in its contents would break the search results if
those contents were part of the results, because we were splitting on colons,
which can't work with untrusted input.

Changing to use the null byte as a separator is much safer.

Closes #42059

Previously, the last push widget would only show when the branch never had
a merge request associated with it - even merged or closed ones. Now the
widget will disregard merge requests that are merged or closed.

see https://gitlab.com/gitlab-org/gitlab-ce/issues/42025

Closes #41633

If we search for notes before the MR was merged, we have to load every commit
that was ever part of the MR, or mentioned in a push. In extreme cases, this can
be tens of thousands of commits to load, but we know they can't revert the merge
commit, because they are from before the MR was merged.

In the (rare) case that we don't have a `merged_at` value for the MR, we can
still search all notes.

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/41956

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/41163

Use simple Next/Prev paging for jobs to avoid large count queries on arbitrarily large sets of historical jobs