Playwright: Convert lazy-loading test to playwright (#11988)

* Implement method to wait for next sync

* Add timeline coded to app page

* Convert network plugin

* Add createBot fixture

* Convert lazy-loading test

* Remove cypress test

* Remove converted files

* Remove imports

* Fix date in copyright header

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

* Fix date in copyright header

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

* Use proper method to send messages

* Fix sliding-sync test

* Address comments

* Move code to timeline

---------

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

playwright/pages/network.ts

@@ -0,0 +1,59 @@
+/*
+Copyright 2023 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 type { Page, Request } from "@playwright/test";
+import type { Client } from "./client";
+
+export class Network {
+    private isOffline = false;
+    private readonly setupPromise: Promise<void>;
+
+    constructor(private page: Page, private client: Client) {
+        this.setupPromise = this.setupRoute();
+    }
+
+    /**
+     * Checks if the request is from the client associated with this network object.
+     * We do this so that other clients (eg: bots) are not affected by the network change.
+     */
+    private async isRequestFromOurClient(request: Request): Promise<boolean> {
+        const accessToken = await this.client.evaluate((client) => client.getAccessToken());
+        const authHeader = await request.headerValue("Authorization");
+        return authHeader === `Bearer ${accessToken}`;
+    }
+
+    private async setupRoute() {
+        await this.page.route("**/_matrix/**", async (route) => {
+            if (this.isOffline && (await this.isRequestFromOurClient(route.request()))) {
+                route.abort();
+            } else {
+                route.continue();
+            }
+        });
+    }
+
+    // Intercept all /_matrix/ networking requests for client and fail them
+    async goOffline(): Promise<void> {
+        await this.setupPromise;
+        this.isOffline = true;
+    }
+
+    // Remove intercept on all /_matrix/ networking requests for this client
+    async goOnline(): Promise<void> {
+        await this.setupPromise;
+        this.isOffline = false;
+    }
+}