Gitaly Server info for admin panel

See merge request gitlab-org/gitlab-ce!16794

Implements the client side for gitlab-org/gitaly#819. Which is a server
info command. This checks the server version and git binairy version on
the server.

A small UI was added for administrators, so they can check the status of
the Gitaly server. This is done for each storage the monolith knows.

Because of this commit, gitlab-org/gitlab-ce!15580 is now closed. That
MR removed the Git version too, but didn't replace it with anything.

The group activity feed was limited to the first 20 projects found
in the group, which caused activity from some projects to be omitted.
A limit of 20 is applied to the query for events, so the
extra pagination does little in the way of performance.

Closes #42560

On epics roadmap page we list all epics in the given time frame
without pagination (at least for the first iteration), in this
case it would be nice to use the existing issuables index logic
except pagination (see MR gitlab-ee!4281). For this reason this
patch allows to easily disable pagination.

Related gitlab-ee!4281

Fix Error 500 when repository has no avatar

Closes #42249

See merge request gitlab-org/gitlab-ce!16601

Otherwise we'd only preload the ancestors that would fit the
page. That way, when a search result was on the first page, but the
ancestor didn't fit the page anymore. We would not have the preloaded
ancestor when rendering the hierarchy.

When searching we would limit the scope of ancestors to load because
the filter would be applied to the ancestors. Instead, we need to load
_all_ ancestors for matching projects.

Resolve "Commits atom feed is double-escaped"

Closes #41208

See merge request gitlab-org/gitlab-ce!16603

Html code now works in commits atom feed `title` and `summary`.

Resolve "Password authentication enabled for Git over HTTP(S) can not be disabled via UI"

Closes #42206

See merge request gitlab-org/gitlab-ce!16577