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/utils/space.tsx

@@ -30,7 +30,6 @@ import { showRoomInviteDialog } from "../RoomInvite";
 import CreateSubspaceDialog from "../components/views/dialogs/CreateSubspaceDialog";
 import AddExistingSubspaceDialog from "../components/views/dialogs/AddExistingSubspaceDialog";
 import defaultDispatcher from "../dispatcher/dispatcher";
-import { RoomViewStore } from "../stores/RoomViewStore";
 import { Action } from "../dispatcher/actions";
 import Spinner from "../components/views/elements/Spinner";
 import { shouldShowComponent } from "../customisations/helpers/UIComponents";
@@ -38,6 +37,7 @@ import { UIComponent } from "../settings/UIFeature";
 import { OpenSpacePreferencesPayload, SpacePreferenceTab } from "../dispatcher/payloads/OpenSpacePreferencesPayload";
 import { OpenSpaceSettingsPayload } from "../dispatcher/payloads/OpenSpaceSettingsPayload";
 import { OpenAddExistingToSpaceDialogPayload } from "../dispatcher/payloads/OpenAddExistingToSpaceDialogPayload";
+import { SdkContextClass } from "../contexts/SDKContext";
 
 export const shouldShowSpaceSettings = (space: Room) => {
     const userId = space.client.getUserId();
@@ -113,7 +113,7 @@ export const showAddExistingSubspace = (space: Room): void => {
         space,
         onCreateSubspaceClick: () => showCreateNewSubspace(space),
         onFinished: (added: boolean) => {
-            if (added && RoomViewStore.instance.getRoomId() === space.roomId) {
+            if (added && SdkContextClass.instance.roomViewStore.getRoomId() === space.roomId) {
                 defaultDispatcher.fire(Action.UpdateSpaceHierarchy);
             }
         },
@@ -125,7 +125,7 @@ export const showCreateNewSubspace = (space: Room): void => {
         space,
         onAddExistingSpaceClick: () => showAddExistingSubspace(space),
         onFinished: (added: boolean) => {
-            if (added && RoomViewStore.instance.getRoomId() === space.roomId) {
+            if (added && SdkContextClass.instance.roomViewStore.getRoomId() === space.roomId) {
                 defaultDispatcher.fire(Action.UpdateSpaceHierarchy);
             }
         },