Store refactor: use non-global stores in components (#9293)

* Add Stores and StoresContext and use it in MatrixChat and RoomView

Added a new kind of class:
- Add God object `Stores` which will hold refs to all known stores and the `MatrixClient`. This object is NOT a singleton.
- Add `StoresContext` to hold onto a ref of `Stores` for use inside components.

`StoresContext` is created via:
- Create `Stores` in `MatrixChat`, assigning the `MatrixClient` when we have one set. Currently sets the RVS to `RoomViewStore.instance`.
- Wrap `MatrixChat`s `render()` function in a `StoresContext.Provider` so it can be used anywhere.

`StoresContext` is currently only used in `RoomView` via the following changes:
- Remove the HOC, which redundantly set `mxClient` as a prop. We don't need this as `RoomView` was using the client from `this.context`.
- Change the type of context accepted from `MatrixClientContext` to `StoresContext`.
- Modify alllll the places where `this.context` is used to interact with the client and suffix `.client`.
- Modify places where we use `RoomViewStore.instance` and replace them with `this.context.roomViewStore`.

This makes `RoomView` use a non-global instance of RVS.

* Linting

* SDKContext and make client an optional constructor arg

* Move SDKContext to /src/contexts

* Inject all RVS deps

* Linting

* Remove reset calls; deep copy the INITIAL_STATE to avoid test pollution

* DI singletons used in RoomView; DI them in RoomView-test too

* Initial RoomViewStore.instance after all files are imported to avoid cyclical deps

* Lazily init stores to allow for circular dependencies

Rather than stores accepting a list of other stores in their constructors,
which doesn't work when A needs B and B needs A, make new-style stores simply
accept Stores. When a store needs another store, they access it via `Stores`
which then lazily constructs that store if it needs it. This breaks the
circular dependency at constructor time, without needing to introduce
wiring diagrams or any complex DI framework.

* Delete RoomViewStore.instance

Replaced with Stores.instance.roomViewStore

* Linting

* Move OverridableStores to test/TestStores

* Rejig how eager stores get made; don't automatically do it else tests break

* Linting

* Linting and review comments

* Fix new code to use Stores.instance

* s/Stores/SdkContextClass/g

* Update docs

* Remove unused imports

* Update src/stores/RoomViewStore.tsx

Co-authored-by: Michael Telatynski <7t3chguy@gmail.com>

* Remove empty c'tor to make sonar happy

Co-authored-by: Michael Telatynski <7t3chguy@gmail.com>

src/stores/widgets/StopGapWidgetDriver.ts

@@ -53,9 +53,9 @@ import { CHAT_EFFECTS } from "../../effects";
 import { containsEmoji } from "../../effects/utils";
 import dis from "../../dispatcher/dispatcher";
 import SettingsStore from "../../settings/SettingsStore";
-import { RoomViewStore } from "../RoomViewStore";
 import { ElementWidgetCapabilities } from "./ElementWidgetCapabilities";
 import { navigateToPermalink } from "../../utils/permalinks/navigator";
+import { SdkContextClass } from "../../contexts/SDKContext";
 
 // TODO: Purge this from the universe
 
@@ -210,7 +210,7 @@ export class StopGapWidgetDriver extends WidgetDriver {
         targetRoomId: string = null,
     ): Promise<ISendEventDetails> {
         const client = MatrixClientPeg.get();
-        const roomId = targetRoomId || RoomViewStore.instance.getRoomId();
+        const roomId = targetRoomId || SdkContextClass.instance.roomViewStore.getRoomId();
 
         if (!client || !roomId) throw new Error("Not in a room or not attached to a client");
 
@@ -291,7 +291,7 @@ export class StopGapWidgetDriver extends WidgetDriver {
 
         const targetRooms = roomIds
             ? (roomIds.includes(Symbols.AnyRoom) ? client.getVisibleRooms() : roomIds.map(r => client.getRoom(r)))
-            : [client.getRoom(RoomViewStore.instance.getRoomId())];
+            : [client.getRoom(SdkContextClass.instance.roomViewStore.getRoomId())];
         return targetRooms.filter(r => !!r);
     }
 
@@ -430,7 +430,7 @@ export class StopGapWidgetDriver extends WidgetDriver {
     ): Promise<IReadEventRelationsResult> {
         const client = MatrixClientPeg.get();
         const dir = direction as Direction;
-        roomId = roomId ?? RoomViewStore.instance.getRoomId() ?? undefined;
+        roomId = roomId ?? SdkContextClass.instance.roomViewStore.getRoomId() ?? undefined;
 
         if (typeof roomId !== "string") {
             throw new Error('Error while reading the current room');