Meek-azure deprecation plan

As meek-azure domain fronting days are counted, I'm opening this ticket to draft a deprecation plan:

1. Remove 'meek-azure' option from Tor Browser for Android and Desktop built-in bridges (cc: Tor Browser Devs).
2. Update Tor user support docs (tpo/web/support and tpo/web/manual).
3. Help users to migrate to secret bridges and/or Snowflake.
4. Since Chinese users rely on meek-azure, we should announce this change on Tor Comms (Twitter, Mastodon) and community channels (IFF mattermost, Tor mailing lists, OONI channel). It would be nice to have the content translated in zh-CN.
5. I don't think Guardian Project is shipping Orbot with meek-azure anymore, but we should ping Nathan.
6. Finally, shutdown meek-azure bridge.