[MM-61588]: Fixed the keyboard interactivity of tablist and added appropriate ARIA properties (#29592)

* [MA-9]: Fixed the keyboard interactivity of tablist and added appropriate ARIA properties

* [MA-9]: Review Fixes: Added aria-level attribute to plugin preferences heading

* [MA-9]: Fixed failing e2e test case

* [MA-9]: Fixed styling in mobile view and fixed failing e2e test cases

* [MA-9]: Minor Refactoring

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

e2e-tests/playwright/support/ui/components/channels/settings/settings_modal.ts

@@ -15,7 +15,7 @@ export default class SettingsModal {
         this.container = container;
 
         this.notificationsSettingsTab = container.locator('#notificationsButton');
-        this.notificationsSettings = new NotificationsSettings(container.locator('#notificationSettings'));
+        this.notificationsSettings = new NotificationsSettings(container.locator('#notificationsSettings'));
     }
 
     async toBeVisible() {