* Remove `controller` and `action` labels from duration histogram.
* Create a new simple counter for `controller` and `action`.
* Adjust histogram buckets to observe smaller response times.

Extend the support for "X-Profile-Token: <token>" to have an additional
header that defines type of profile we are looking for, like:
  X-Profile-Mode: execution
  X-Profile-Mode: memory

Use a full real-world example that is compatible with the omnibus
dashboards and follows Prometheus best practices.

Removing extra blank lines in docs that serve
no purpose, as well as some --- lines that also
are not needed.

Many code blocks are 4spaced, and they render in GitLab
without coloring as a result, even though they are
fenced with a language label. If in a list, other items
will render as being in a code block too, even if not
meant to. This fixes all these issues for many admin
docs (part 2)

Previously, we used brackets to denote the tier badges,
but this made Kramdown, the docs site Markdown renderer,
show many warnings when building the site. This is now
fixed by using parentheses instead of square brackets.

This was caused by [PREMIUM] looking like a link to
Kramdown, which couldn't find a URL there.

See:
- https://gitlab.com/gitlab-com/gitlab-docs/merge_requests/484
- https://gitlab.com/gitlab-org/gitlab-ce/issues/63800

First MR in a series updating all redirected links
in CE documentation to the destination URLs

Previously we were recording process start time as seconds from boot.
This makes it so we record as epoch time.