If the "Frequently visited" list needs more space than the given, its content is now scrollable. 
This only affects the "Frequently visited" not the search results.

Rename classes to (hopefully) clearer names while we're doing that.

This prepares the codebase for a Gitaly migration. See
https://gitlab.com/gitlab-org/gitaly/issues/553

This reverts merge request !14768

We were looking these up on each request to an issue page, because the form is
pre-filled, as is the template dropdown. That was unnecessary: we could just
treat these as 'special' repository files (like the rendered README) and cache
them in Redis until they change on a push.

The basename appears to have been a holdover from the past - it doesn't look
necessary now. Some of the regexes were unanchored on one side, so explicitly
ensure that they only match the root.

Apart from that, this means that pushing to foo/README.md will no longer
invalidate the main README cache for a project.

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/38871

Collect usage pings `Gcp::Cluster.enabled` and `Gcp::Cluster.disabled`, instead of `Gcp::Cluster.count`