Use get_current_users_in_room from store and not StateHandler (#9910)

changelog.d/9910.bugfix

changelog.d/9910.feature

synapse/handlers/directory.py

synapse/handlers/events.py

synapse/handlers/message.py

synapse/handlers/presence.py

synapse/handlers/room.py

synapse/handlers/sync.py

synapse/state/__init__.py

synapse/storage/_base.py

synapse/storage/databases/main/roommember.py

synapse/storage/databases/main/user_directory.py