Tutorials use future tense, so let's build in the expectation that
we will turn off alerts for future tense on those pages.

Rename index.md to _index.md and update crosslinks
from other docs and code files.

Changelog: changed

Also rename index files for user/namespace, user/operations_dashboard,
and user/organization, and update crosslinks.

Rename files in doc/tutorials/ and fix all links.

H1 headers needs to be in YAML frontmatter now

Update offering notes with all three offerings

Co-authored-by: Lysanne Pinto <lpinto@gitlab.com>

Related to: https://gitlab.com/gitlab-org/gitlab/-/issues/439130

Because for now, we're changing the format.

Related to: https://gitlab.com/gitlab-org/gitlab-docs/-/issues/1751

Update the links in all docs except user and admin pages

Because the left nav is changing
and will have a button instead
of carat, and no magnifying glass.

Related to: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/127935

Because we changed the way we
do the markdown.

Related to: https://gitlab.com/gitlab-org/gitlab-docs/-/issues/1690