These are all over the place, but several are of interest to the
Chief of Staff team.

Because any maintainer can merge
Related to: https://gitlab.com/gitlab-org/gitlab/-/issues/397788

PG12 was dropped in GitLab 16.0 release.

Can we make this regex less greedy while still checking multi-line
curl strings?

- Add quick start guide for postgres.ai web interface
- #database-lab was deprecated in favor of the web interface
- Removed references to getting explain plans from chatops

Polishes text, cross-links, capitalizes Database Lab. Fixes
punctuation and the language specified in a few code blocks.

Related epic: https://gitlab.com/groups/gitlab-com/-/epics/1940

This was missing before and it took me some time to figure it out.
It's not obvious either because we don't use `gitlabhq_dblab` as
the DB name in production.

In https://gitlab.com/gitlab-com/www-gitlab-com/-/merge_requests/104673,
we split the Enablement stage into Systems and Data Stores. This commit
changes the Database group to the Data Stores stage.

This change adds developer documentation on how to access and
use database lab and postgres.ai

Relates to https://gitlab.com/gitlab-org/database-team/team-tasks/-/issues/211