Return RLS instance through function to avoid import side effect (#31091)

* Attach function that returns instance

So that just importing this file does not create a RLS instance.

* Fix jest test

test/unit-tests/components/viewmodels/roomlist/RoomListHeaderViewModel-test.tsx

@@ -48,6 +48,9 @@ describe("useRoomListHeaderViewModel", () => {
     beforeEach(() => {
         matrixClient = stubClient();
         space = mkStubRoom("spaceId", "spaceName", matrixClient);
+        jest.spyOn(SettingsStore, "getValue").mockImplementation((name: string): any => {
+            if (name === "RoomList.preferredSorting") return SortingAlgorithm.Recency;
+        });
     });
 
     afterEach(() => {