Add mention and warning about ACME v1 deprecation to the TLS config

We do this by moving the recursive query to be fully in the DB.

Update INSTALL.md to recommend reverse proxying and warn about ACMEv1 deprecation

Stop sending events when creating or deleting associations (room aliases). Send an updated canonical alias event if one of the alt_aliases is deleted.

Lots of people seem to get confused by this mode, and it's been deprecated
since Synapse 1.1.0. It's time for it to go.

Add typing information to the spam checker modules.

Signed-off-by: Fridtjof Mund <fridtjof@das-labor.org>

Fixes #6916.

Convert directory handler tests to use HomeserverTestCase.

Add a method to the spam checker to filter the user directory results.

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

Add documentation for the spam checker.

Update ACME.md to mention ACME v1 deprecation

Fixes #5528

Spell out that the last event sent to a room won't be deleted by a purge