Fix inserting bytes as text in `censor_redactions`

Co-Authored-By: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

Factor out backgroung updates

Fixes #6109

* Remove unused public room list timeout param

* Add changelog

* Fix /federation/v1/state for recent room versions

Turns out this endpoint was completely broken for v3 rooms. Hopefully this
re-signing code is irrelevant nowadays anyway.

Don't regenerate numeric user ID if registration fails.

This prevents us logging "Responding to media request with responder %s".

Fix unique_user_filter_index schema update

Cache room membership lookups in _get_joined_users_from_context

Don't 500 when trying to exchange a revoked 3PID invite

Pillow will use nearest neighbour as the resampling algorithm if the
source image is either 1-bit or a color palette using 8 bits. If we
convert to RGB before scaling, we'll probably get a better result.