discuss TPA-RFC-36: gitolite and gitweb migration to GitLab

In #40472 (closed) and gitlab#36 (moved), we had lengthy discussions on how we could possibly migrate everything to GitLab already, and came up with a proposal.

Those tickets are very long, however, and basically summarized in the TPA-RFC-36 proposal. This is therefore a new ticket aimed at receiving feedback on the proposal.

the full text of the proposal was sent to tor-internal and is also available in here:

https://gitlab.torproject.org/tpo/tpa/team/-/wikis/policy/tpa-rfc-36-gitolite-gitweb-retirement

Summary: Gitolite (git.torproject.org and git-rw.torproject.org) and GitWeb (https://gitweb.torproject.org) will be fully retired within 9 to 12 months (by the end of Q2 2024). TPA will implement redirections on the web interfaces to maintain limited backwards compatibility for the old URLs. Start migrating your repositories now by following the migration procedure.

checklist of tasks to be done after this is adopted:

• create issues for each step in the timeline
• update wiki page to reflect the adoption