Implement new EE-only system note icons

Closes #3205

See merge request !2713

Log Geo file download attempts and status

See merge request !2722

Remove unneeded sidebar class

Closes #3218

See merge request !2738

Add note about restarting repmgrd to ensure it doesn't think it's a
master

Break out configuration, and commands needed into their own sections.

* Clean up section on pgbouncer user information

* Update formatting
* Explain more about prerequisites

* Change layout to clarify differenet stages of the install
* Add instructions for pgbouncer and gitlab-rails
* Remove requirement for database user password.
* repmgrd is automatically setup now, so remove manual steps

EEP only

This reflects the current state of the repmgr in omnibus-gitlab MR 1664

Add the ability to add values to Metric events

See merge request !2730

Fix typo for slot name.

See merge request !2737

[EE] Gitaly apply gitattributes

See merge request !2702

Fix advanced search syntax for commits

Closes #3011

See merge request !2709

[ci skip]

[ci skip]

Extend documentation on writing EE features

See merge request !2248

Used to guard EE-licensed features.

CE upstream: Friday

Closes gitaly#464, gitlab-com/community-writers#40, gitlab-ce#36618, gitaly#468, #3149, gitlab-ce#36492, and gitlab-ce#3646

See merge request !2710

* ee/master:
  Geo - Remove unnecessary param from Geo::BaseSyncService#update_registry
  [ci skip] Geo: add documentation on what selective replication support
  Update multi_project_pipeline_graphs.md
  Drop unnecessary timestamp columns in Geo event tables

[ci skip] Geo: add documentation on what selective replication support

Closes #3161

See merge request !2734

Geo - Remove unnecessary param from Geo::BaseSyncService#update_registry

See merge request !2735