Add initial filtering support to new room list

For https://github.com/vector-im/riot-web/issues/13635

This is an incomplete implementation and is mostly dumped in this state for review purposes. The remainder of the features/bugs are expected to be in more bite-sized chunks.

This exposes the RoomListStore on the window for easy access to things like the new filter functions (used in debugging).

This also adds initial handling of "new rooms" to the client, though the support is poor.

Known bugs:
* [ ] Regenerates the entire room list when a new room is seen.
* [ ] Doesn't handle 2+ filters at the same time very well (see gif. will need a priority/ordering of some sort).
* [ ] Doesn't handle room order changes within a tag yet, despite the docs implying it does.

src/utils/IDisposable.ts

@@ -0,0 +1,19 @@
+/*
+Copyright 2020 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+export interface IDisposable {
+    dispose(): void;
+}