refactor: Promote handling unsigned data out of timeline

Also fixes:
- Transaction IDs leaking in event route
- Age not being set for event relations or threads
- Both of the above for search results

Notes down concern with relations table

src/api/client/sync/v3/state.rs

@@ -127,7 +127,7 @@ pub(super) async fn build_state_incremental<'a>(
 		let last_pdu_of_last_sync = services
 			.rooms
 			.timeline
-			.pdus_rev(Some(sender_user), room_id, Some(last_sync_end_count.saturating_add(1)))
+			.pdus_rev(room_id, Some(last_sync_end_count.saturating_add(1)))
 			.boxed()
 			.next()
 			.await