Fix links as discovered by the lint in the docs project

These were disabled in production mode, but that also broke the rest of
the performance bar. As they were only enabled in development mode, we
can just remove them for now.

Red Hat finally fixed the NFS server delegation problem that caused the
TEST_STATEID flood. Mention the docs that disabling delegation may
no longer be needed.

* Added elasticsearch.md
* Added reference to guide in Troubleshooting section

MD002 - First header should be level 1
MD006 - Start bullets at beginning of line
MD019 - No multiple spaces after header style
MD022 - Headers surrounded by blank lines
MD025 - Only 1 level 1 header
MD028 - No blank lines within blockquote
MD038 - Spaces inside code span elements

I'm adding some wording to our hardware requirements to explain that needs vary
by workload. I also included some examples of factors that may influence the
workload.

We recommend avoiding CephFS https://docs.gitlab.com/ee/administration/high_availability/nfs.html#avoid-using-cephfs-and-glusterfs

* Use `GiB memory` to describe memory needs.
* Add local storage recommendation for monitoring node.
* Better align CPU/Memory to match common cloud provider instnace types.
* Update requirements based on the new 10k user standard.

1. The output isn't great. It can be hard to find hotspots and, even
   when you do find them, to find why those are hotspots.
2. It uses some jQuery-specific frontend code which we can remove now
   that we don't have this any more.
3. It's only possible to profile the initial request, not any subsequent
   AJAX requests.

This change adds audit events for
download of repository and export of
project.

Some markdown headers needed tweaking to adhere
to standards, including blank lines above and below,
only one space after hash, first header should be
h1, and only one h1 per doc

A project can have the same `LfsObject` linked with up to three
`LfsObjectsProject` records. Each of these records would be for a
different repository, recorded in the `repository_type` property. The
different repositories at time of writing are "project", "wiki", and
"design". See https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/13894

This change exports the list of `repository_type`s as a JSON mapping of
oid => repository_types, which are imported to recreate the correct
`LfsObjectsProject` records.

https://gitlab.com/gitlab-org/gitlab-ee/issues/11090

This change adds audit logs for user impersonation
when an admin starts/stops impersonating
another user.

This will make it easier to parse this in production and adds the
`correlation_id` if available.

Correct the spacing of unordered markdown lists
in docs, to maintain standards of documentation,
in /user and others.

* 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.

Ensure that all numbered lists use only 1. and no other numbers.
Also ensure that numbered lists use proper spacing.

- Add missing path to Gitaly configuration
- Properly list steps for Gitaly configurations
- Move sections around

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

Correct the spacing of unordered markdown lists
in docs, to maintain standards of documentation.

Related issues:

* https://github.com/fog/fog-aws/issues/523
* https://gitlab.com/gitlab-org/gitlab-ce/issues/63041

* Add deprecation warning to old integration
* Add user docs
* Add admin docs