Make several links, mostly in admin troubleshooting,
relative, as is the standard

Move Gitlab::SidekiqMonitor to namespace Gitlab::SidekiqDaemon::Monitor
 - Class name and file name change
 - File path change to lib/gitlab/sidekiq_daemon/monitor.rb
 - Update class usage/reference in other files, including documentation

It consists of two parts:

1. Redirecting users to the configured external storage
1. Allowing the external storage to request the static object(s)
   on behalf of the user by means of specific tokens

Part of https://gitlab.com/gitlab-com/gl-infra/infrastructure/issues/6829

- minor style corrections
- document rsa keys limitation

The database load balancing docs had some mention of the logs that
needed to be updated, and the logs doc had an absolute link to
gitlab.com instead of a relative link to a markdown file.

Those feature flags were always enabled so we can remove them safely.

Move rails and linux cheat sheets, and test_environment
reference docs to the docs project

To emphasize the happy path for updating Geo nodes, put the version
specific steps in a separate document and cross-link them for
discoverability.

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/11881

Signed-off-by: NRémy Coutable <remy@rymai.me>

Signed-off-by: NBalasankar "Balu" C <balasankar@gitlab.com>

Clean up issues that may cause the docs-lint
test to fail, such as trailing whitespace, no
EOF newline, blockquotes, etc

Change from ruby mdl to node markdownlint, add
config file to root of project, delete old config
file, update exceptions, and fix one doc that
was didn't meet standards

Square and Angle bracket use causes kramdown warnings,
so changed or enclosed in backticks as needed

related to https://gitlab.com/gitlab-org/gitlab-ce/issues/65422

The flag defaulted to true, so there's no change unless users turned it
off. Given there's a lack of issues regarding object pools, this should
be OK.

- Strikeout for metrics that aren't reported anymore

- added 👍 for all the metrics that appear to be still
  available

- Added 🆕 for the new metrics.

- Determine Release when the new metrics appeared

- Add descriptions for the new metrics

- remove the adornments 🆕 and 👍

- removce the lines with strikeout