Make cleaning up pushers depend on the device_id instead of the token_id (#15280)

This makes it so that we rely on the `device_id` to delete pushers on logout,
instead of relying on the `access_token_id`. This ensures we're not removing
pushers on token refresh, and prepares for a world without access token IDs
(also known as the OIDC).

This actually runs the `set_device_id_for_pushers` background update, which
was forgotten in #13831.

Note that for backwards compatibility it still deletes pushers based on the
`access_token` until the background update finishes.

tests/replication/test_pusher_shard.py

@@ -51,12 +51,12 @@ class PusherShardTestCase(BaseMultiWorkerStreamTestCase):
             self.hs.get_datastores().main.get_user_by_access_token(access_token)
         )
         assert user_dict is not None
-        token_id = user_dict.token_id
+        device_id = user_dict.device_id
 
         self.get_success(
             self.hs.get_pusherpool().add_or_update_pusher(
                 user_id=user_id,
-                access_token=token_id,
+                device_id=device_id,
                 kind="http",
                 app_id="m.http",
                 app_display_name="HTTP Push Notifications",