Query rooms with ACLs instead of all rooms (#3338)

This now should actually speed up startup times.
This is because _many_ rooms (like DMs) don't have room ACLs, this means
that we had around 95% pointless DB queries. (as queried on d.m.org)

roomserver/internal/query/query.go

@@ -1099,3 +1099,8 @@ func (r *Queryer) QueryUserIDForSender(ctx context.Context, roomID spec.RoomID,
 
 	return nil, nil
 }
+
+// RoomsWithACLs returns all room IDs for rooms with ACLs
+func (r *Queryer) RoomsWithACLs(ctx context.Context) ([]string, error) {
+	return r.DB.RoomsWithACLs(ctx)
+}