Add federation modes: temporarily paused, allow-listed-only & consent-based

[mayel]

• Temporarily paused: Store activities to be pushed to the fediverse and remote activities received in a queue, to be processed when federation is switched back to automatic
• Allow-listed only: Only federate domains/actors added to allow-lists by mods or individual user
• Consent-based: hold the processing of federation activities in a queue until a rule is created for an unknown domain or actor (either explicitly allowing it or explicitly blocking it) by a mod or relevant user

Required work:

• Add a way to specifically allow-list remote domains/users for federation #1038
• UI to view the federation processing queue, with buttons to process immediately or to ignore/delete/allow-list/deny-list/etc #1037
• Ability to pause/restart job queues (when federation is paused instance-wide)
• Setting for user to pause their federation, which should be checked before processing their activities (meaning their outgoing activities, and any incoming follows/mentions/DMs - they may still see new remote public activities in feeds)