RoomListViewModel: Support primary filters in the view model (#29454)

* Track available filters and expose this info from the vm

- Adds a separate hook that tracks the filtered rooms and the available
  filters.
- When secondary filters are added, some of the primary filters will be
  selectively hidden. So track this info in the vm.

* Write tests

* Fix typescript error

* Fix translation

* Explain what a primary filter is

src/i18n/strings/en_EN.json

@@ -2099,6 +2099,12 @@
         "failed_add_tag": "Failed to add tag %(tagName)s to room",
         "failed_remove_tag": "Failed to remove tag %(tagName)s from room",
         "failed_set_dm_tag": "Failed to set direct message tag",
+        "filters": {
+            "favourite": "Favourites",
+            "people": "People",
+            "rooms": "Rooms",
+            "unread": "Unread"
+        },
         "home_menu_label": "Home options",
         "join_public_room_label": "Join public room",
         "joining_rooms_status": {