Merge branch 'aqualls-revamp-testing-section' into 'master'

Restructure and split docs testing pages

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/145054



Merged-by: Evan Read <eread@gitlab.com>
Approved-by: Evan Read <eread@gitlab.com>
Co-authored-by: Amy Qualls <aqualls@gitlab.com>