Allow non-member state sent in room batch to resolve for historic events

Part of #12110

Complement test: matrix-org/complement#354

Previously, they didn't resolve because async `filter_events_for_client`
removes all outlier state except for out-of-band membership.

Author: MadLittleMods

synapse/handlers/room_batch.py

@@ -213,9 +213,6 @@ async def persist_state_events_at_start(
                     room_id=room_id,
                     action=membership,
                     content=event_dict["content"],
-                    # Mark as an outlier to disconnect it from the normal DAG
-                    # and not show up between batches of history.
-                    outlier=True,
                     historical=True,
                     # Only the first event in the state chain should be floating.
                     # The rest should hang off each other in a chain.
@@ -246,9 +243,6 @@ async def persist_state_events_at_start(
                         state_event["sender"], app_service_requester.app_service
                     ),
                     event_dict,
-                    # Mark as an outlier to disconnect it from the normal DAG
-                    # and not show up between batches of history.
-                    outlier=True,
                     historical=True,
                     # Only the first event in the state chain should be floating.
                     # The rest should hang off each other in a chain.