Update links in /geo /high_availability and /ci

Fix as many backtick and capitalization issues as
possible in Geo and HA docs

As part of https://gitlab.com/gitlab-org/gitlab-ce/issues/61704 we want
to rename gitlab-monitor to gitlab-exporter, to be less confusing and
better align with naming conventions in the community.

This changes any mention of gitlab-ce to gitlab-foss, and any mention of
gitlab-ee to just gitlab.

- Make sure we have type defined in the frontmatter
- Add troubleshooting sections where absent
- Meaningful intros where absent

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 in /high_availability and /auth (part 1)

The installation link has changed from /installation/ to /install/. This
commit will update all the remaining links that are missing.

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

Add backticks around square brackets, or fix links, as necessary.

Linting rule not enabled for now
because tooling produces false
positives.

There are several instances in our HA docs where an example of
`Y.Y.Y.Y consul1.gitlab.example.com Z.Z.Z.Z` is given,
but this value isn't explicitly stated. It should be
the IP addresses or DNS records of the Consul server nodes.

Updating documentation to include
Prometheus Service Discovery. Added
monitoring node documentaiton as
well as documentation for the
individual service nodes.

Adding password in the Redis Sentinel config does not actually work
because v3.2.x doesn't respond to the `AUTH` command.

This came up in
https://gitlab.com/gitlab-org/omnibus-gitlab/issues/4126.

Update across various scaling/HA documentation to make the layout
more clear. This sets the stage/format for more changes in the
future.

For the sake of consistency, removes any extraneous
consecutive blank lines from the doc suite.

For the sake of consistency, removes any extraneous
consecutive blank lines from the doc suite.

- Also makes other minor Markdown fixes that were near the main fixes.

- Also makes other minor Markdown fixes that were near the main fixes.