Align on GitLab High Availability naming and terminology

We have Geo HA and Gitaly HA, yet HA is more of a methodology, not a specific feature. Using HA in a feature name also isn't MECEFU.

Let's use this issue to brainstorm on better ways to market and name these features.

cc @jramsay @fzimmer @joshlambert

Locations

• Gitaly
• Geo
• Postgres HA - @ljlane gitlab-org/gitlab#221110 (closed)
• Premium Support - www-gitlab-com!37448 (diffs)