Enable Faster Remote Room Joins against worker-mode Synapse. (#14752)

* Enable Complement tests for Faster Remote Room Joins on worker-mode

* (dangerous) Add an override to allow Complement to use FRRJ under workers

* Newsfile

Signed-off-by: Olivier Wilkinson (reivilibre) <oliverw@matrix.org>

* Fix race where we didn't send out replication notification

* MORE HACKS

* Fix get_un_partial_stated_rooms_token to take instance_name

* Fix bad merge

* Remove warning

* Correctly advance un_partial_stated_room_stream

* Fix merge

* Add another notify_replication

* Fixups

* Create a separate ReplicationNotifier

* Fix test

* Fix portdb

* Create a separate ReplicationNotifier

* Fix test

* Fix portdb

* Fix presence test

* Newsfile

* Apply suggestions from code review

* Update changelog.d/14752.misc

Co-authored-by: Erik Johnston <erik@matrix.org>

* lint

Signed-off-by: Olivier Wilkinson (reivilibre) <oliverw@matrix.org>
Co-authored-by: Erik Johnston <erik@matrix.org>

docker/complement/conf/workers-shared-extra.yaml.j2

@@ -94,10 +94,8 @@ allow_device_name_lookup_over_federation: true
 experimental_features:
   # Enable history backfilling support
   msc2716_enabled: true
-  {% if not workers_in_use %}
   # client-side support for partial state in /send_join responses
   faster_joins: true
-  {% endif %}
   # Enable support for polls
   msc3381_polls_enabled: true
   # Enable deleting device-specific notification settings stored in account data