collab ui: Dismiss project shared notifications when leaving room (#10160)

When leaving a call/room in which a project was shared, the shared
project notification was not getting dismissed when the person that
shared the project left the room.
Although there was a `cx.emit(Event::Left)` call inside room, the event
was never received in the `project_shared_notification` module, because
the room is dropped before the event can be dispatched. Moving the
`cx.emit(Event::Left)` to the active call fixed the problem. Also
renamed `Event::Left` to `Event::RoomLeft` because the room join
equivalent is also called `Event::RoomJoined`.


Release Notes:

- Fixed project shared notification staying open, when the user that
shared the project left the room

crates/call/src/call.rs

@@ -373,7 +373,10 @@ impl ActiveCall {
         self.report_call_event("hang up", cx);
 
         Audio::end_call(cx);
+
+        let channel_id = self.channel_id(cx);
         if let Some((room, _)) = self.room.take() {
+            cx.emit(Event::RoomLeft { channel_id });
             room.update(cx, |room, cx| room.leave(cx))
         } else {
             Task::ready(Ok(()))