Handle SDKContextClass client initialisation internally (#34146)

* Handle SDKContextClass `client` initialisation internally

Rather than via MatrixChat - this is predominantly for Lifecycle tests as they don't use a MatrixChat and it doesn't make much sense for this component to own this state.

* Fix tests

apps/web/test/unit-tests/utils/exportUtils/HTMLExport-test.ts

@@ -33,6 +33,7 @@ import DMRoomMap from "../../../../src/utils/DMRoomMap";
 import { mediaFromMxc } from "../../../../src/customisations/Media";
 import SettingsStore from "../../../../src/settings/SettingsStore";
 import { SDKContextClass } from "../../../../src/contexts/SDKContextClass";
+import { TestSDKContext } from "../../TestSDKContext.ts";
 
 jest.mock("jszip");
 jest.mock("../../../../src/settings/SettingsStore");
@@ -93,6 +94,7 @@ const EVENT_MENTION: IRoomEvent = {
 describe("HTMLExport", () => {
     let client: jest.Mocked<MatrixClient>;
     let room: Room;
+    let sdkContext: TestSDKContext;
 
     filterConsole(
         "Starting export",
@@ -111,7 +113,10 @@ describe("HTMLExport", () => {
         jest.setSystemTime(REPEATABLE_DATE);
 
         client = stubClient() as jest.Mocked<MatrixClient>;
-        SDKContextClass.instance.client = client;
+        sdkContext = new TestSDKContext();
+        // @ts-ignore HTMLExport uses SDKContext in the constructor
+        SDKContextClass.instance = sdkContext;
+        sdkContext._client = client;
         DMRoomMap.makeShared(client);
 
         room = new Room("!myroom:example.org", client, "@me:example.org");