Show spaces horizontal bar

### Summary

This merge request adds a horizontal bar at top of room list, which shows spaces. By clicking on a space, user can filter out rooms belonging only to that specific space.

### Pending/ Help needed

#### Segfault when loading active connection on startup

Refer `void SortFilterRoomListModel::cacheSpaceHierarchy()` ([link](8c372800d7 (b969e462c30df43ef3714ea441948d8d8027f6a0_117_126))) in `src/sortfilterroomlistmodel.cpp`.

On [line 129](8c372800d7 (b969e462c30df43ef3714ea441948d8d8027f6a0_117_129)), I have called `connection->allRooms()`, which segfaults if the active connection hasn't been loaded yet. Is there a way to ensure that `Controller::instance().activeConnection()` on line 128 waits till connection is loaded?

#### Avatars

Avatars on space horizontal bar aren't aligned to vertical middle. I'll need help with that. 

Using the code below doesn't help with padding

```qml
delegate: QQC2.Control {
    topPadding: 10
    contentItem: Kirigami.Avatar { ..... }
}
```

This complains about uninitialized properties in `Kirigami.Avatar`. (`id`, `currentRoom`, `avatar`, `index` are properties utilized during run time)

After we get around these two issue, this MR will be ready from my side.

src/neochatroom.cpp

@@ -30,6 +30,7 @@
 #include "events/accountdataevents.h"
 #include "events/reactionevent.h"
 #include "events/roomcanonicalaliasevent.h"
+#include "events/roomcreateevent.h"
 #include "events/roommessageevent.h"
 #include "events/roompowerlevelsevent.h"
 #include "events/typingevent.h"
@@ -869,3 +870,17 @@ void NeoChatRoom::clearInvitationNotification()
 {
     NotificationsManager::instance().clearInvitationNotification(id());
 }
+
+bool NeoChatRoom::isSpace()
+{
+    const auto creationEvent = this->creation();
+    if (!creationEvent) {
+        return false;
+    }
+
+#ifdef QUOTIENT_07
+    return creationEvent->roomType() == RoomType::Space;
+#else
+    return false;
+#endif
+}