MM-62558 Add E2E tests for custom profile settings (#30722)

* add e2e tests for custom profile settings

* fix failed tests

* reorg folder and file convention, and add more details of the tests

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

e2e-tests/playwright/specs/functional/channels/notifications/notification.spec.ts

@@ -42,14 +42,14 @@ test('MM-T483 Channel-wide mentions with uppercase letters', async ({pw, headles
     expect(notification.silent).toBe(false);
 
     // Verify the last post as viewed by the regular user in the "off-topic" channel contains the message and is highlighted
-    const otherLastPost = await otherChannelsPage.centerView.getLastPost();
+    const otherLastPost = await otherChannelsPage.getLastPost();
     await otherLastPost.toContainText(message);
     await expect(otherLastPost.container.locator('.mention--highlight')).toBeVisible();
     await expect(otherLastPost.container.locator('.mention--highlight').getByText('@ALL')).toBeVisible();
 
     // Admin navigates to the "off-topic" channel and verifies the message is posted and highlighted correctly
     await adminChannelsPage.goto(team.name, 'off-topic');
-    const adminLastPost = await adminChannelsPage.centerView.getLastPost();
+    const adminLastPost = await adminChannelsPage.getLastPost();
     await adminLastPost.toContainText(message);
     await expect(adminLastPost.container.locator('.mention--highlight')).toBeVisible();
     await expect(adminLastPost.container.locator('.mention--highlight').getByText('@ALL')).toBeVisible();