Include thread replies in message previews (#10631)

* Include thread replies to message previews

* Extend tests

* Fix type issue

* Use currentColor for thread icon

* Fix long room name overflow

* Update snapshots

* Fix preview

* Fix typing issue

* Fix type issues

* Tweak thread reply detection

* Extend tests

* Fix type issue

* Fix test

test/test-utils/threads.ts

@@ -135,6 +135,11 @@ export const mkThread = ({
     }
 
     const thread = room.createThread(rootEvent.getId()!, rootEvent, events, true);
+
+    events.forEach((event) => {
+        thread.timeline.push(event);
+    });
+
     // So that we do not have to mock the thread loading
     thread.initialEventsFetched = true;