Fix user cache acting incorrectly with evictions

The first issue involved copied users which would lead to user updates
causing faster evictions of the cache than was expected.

The second issue involved users that weren't bound to an internal
lifetime eviction policy. These users would not get evicted.
For example, a user without mutual guilds or being part of the internal
cache in general (messages, DMs) would never end up being evicted for
some strange reason. To handle this case, store_user would get a
counterpart named create_user which would create a user without
potentially storing them in the cache. That way only users with a
bound lifetime within the library would be stored.

discord/state.py

@@ -178,7 +178,7 @@ class ConnectionState:
         self._intents = intents
 
         if not intents.members or cache_flags._empty:
-            self.store_user = self.store_user_no_intents
+            self.store_user = self.create_user
             self.deref_user = self.deref_user_no_intents
 
         self.parsers = parsers = {}
@@ -284,7 +284,7 @@ class ConnectionState:
     def deref_user(self, user_id):
         self._users.pop(user_id, None)
 
-    def store_user_no_intents(self, data):
+    def create_user(self, data):
         return User(state=self, data=data)
 
     def deref_user_no_intents(self, user_id):