Add missing type hints to handlers and fix a Spam Checker type hint. (#9896)

The user_may_create_room_alias method on spam checkers
declared the room_alias parameter as a str when in reality it is
passed a RoomAlias object.

synapse/handlers/room_member.py

@@ -1044,7 +1044,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
 
 
 class RoomMemberMasterHandler(RoomMemberHandler):
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
 
         self.distributor = hs.get_distributor()