Initial breakout for room list rewrite

This does a number of things (sorry):
* Estimates the type changes needed to the dispatcher (later to be replaced by https://github.com/matrix-org/matrix-react-sdk/pull/4593)
* Sets up the stack for a whole new room list store, and later components for usage.
* Create a proxy class to ensure the app still functions as expected when the various stores are enabled/disabled
* Demonstrates a possible structure for algorithms

src/components/views/rooms/RoomList2.tsx

@@ -0,0 +1,130 @@
+/*
+Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2017, 2018 Vector Creations Ltd
+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.
+*/
+
+import * as React from "react";
+import { _t } from "../../../languageHandler";
+import { Layout } from '../../../resizer/distributors/roomsublist2';
+import { RovingTabIndexProvider } from "../../../accessibility/RovingTabIndex";
+import { ResizeNotifier } from "../../../utils/ResizeNotifier";
+import RoomListStore from "../../../stores/room-list/RoomListStore2";
+
+interface IProps {
+    onKeyDown: (ev: React.KeyboardEvent) => void;
+    onFocus: (ev: React.FocusEvent) => void;
+    onBlur: (ev: React.FocusEvent) => void;
+    resizeNotifier: ResizeNotifier;
+    collapsed: boolean;
+    searchFilter: string;
+}
+
+interface IState {
+}
+
+// TODO: Actually write stub
+export class RoomSublist2 extends React.Component<any, any> {
+    public setHeight(size: number) {
+    }
+}
+
+export default class RoomList2 extends React.Component<IProps, IState> {
+    private sublistRefs: { [tagId: string]: React.RefObject<RoomSublist2> } = {};
+    private sublistSizes: { [tagId: string]: number } = {};
+    private sublistCollapseStates: { [tagId: string]: boolean } = {};
+    private unfilteredLayout: Layout;
+    private filteredLayout: Layout;
+
+    constructor(props: IProps) {
+        super(props);
+
+        this.loadSublistSizes();
+        this.prepareLayouts();
+    }
+
+    public componentDidMount(): void {
+        RoomListStore.instance.addListener(() => {
+            console.log(RoomListStore.instance.orderedLists);
+        });
+    }
+
+    private loadSublistSizes() {
+        const sizesJson = window.localStorage.getItem("mx_roomlist_sizes");
+        if (sizesJson) this.sublistSizes = JSON.parse(sizesJson);
+
+        const collapsedJson = window.localStorage.getItem("mx_roomlist_collapsed");
+        if (collapsedJson) this.sublistCollapseStates = JSON.parse(collapsedJson);
+    }
+
+    private saveSublistSizes() {
+        window.localStorage.setItem("mx_roomlist_sizes", JSON.stringify(this.sublistSizes));
+        window.localStorage.setItem("mx_roomlist_collapsed", JSON.stringify(this.sublistCollapseStates));
+    }
+
+    private prepareLayouts() {
+        this.unfilteredLayout = new Layout((tagId: string, height: number) => {
+            const sublist = this.sublistRefs[tagId];
+            if (sublist) sublist.current.setHeight(height);
+
+            // TODO: Check overflow
+
+            // Don't store a height for collapsed sublists
+            if (!this.sublistCollapseStates[tagId]) {
+                this.sublistSizes[tagId] = height;
+                this.saveSublistSizes();
+            }
+        }, this.sublistSizes, this.sublistCollapseStates, {
+            allowWhitespace: false,
+            handleHeight: 1,
+        });
+
+        this.filteredLayout = new Layout((tagId: string, height: number) => {
+            const sublist = this.sublistRefs[tagId];
+            if (sublist) sublist.current.setHeight(height);
+        }, null, null, {
+            allowWhitespace: false,
+            handleHeight: 0,
+        });
+    }
+
+    private collectSublistRef(tagId: string, ref: React.RefObject<RoomSublist2>) {
+        if (!ref) {
+            delete this.sublistRefs[tagId];
+        } else {
+            this.sublistRefs[tagId] = ref;
+        }
+    }
+
+    public render() {
+        return (
+            <RovingTabIndexProvider handleHomeEnd={true} onKeyDown={this.props.onKeyDown}>
+                {({onKeyDownHandler}) => (
+                    <div
+                        onFocus={this.props.onFocus}
+                        onBlur={this.props.onBlur}
+                        onKeyDown={onKeyDownHandler}
+                        className="mx_RoomList"
+                        role="tree"
+                        aria-label={_t("Rooms")}
+                        // Firefox sometimes makes this element focusable due to
+                        // overflow:scroll;, so force it out of tab order.
+                        tabIndex={-1}
+                    >{_t("TODO")}</div>
+                )}
+            </RovingTabIndexProvider>
+        );
+    }
+}