* Bump taskgraph to latest revision

* Change Flank url

The repository moved from github.com/TestArmada/flank to
github.com/Flank/flank, and the curl command in the ui-tests Dockerfile
currently fails because of the redirection.

This is an initial instrumented test for Fenix
that checks if a 'baseline' ping is generated when
going to background.

Closes #5630, #6069, #6092, #6091, #6124, and #6147.

Co-authored-by: Simon Chae <chaesmn@gmail.com>
Co-authored-by: Arturo Mejia <arturomejiamarmol@gmail.com>
Co-authored-by: Christian Sadilek <christian.sadilek@gmail.com>
Co-authored-by: Gabriel Luong <gabriel.luong@gmail.com>

Also closes #6250, since we rely solely on the SDK itself to consume the
messages straight from FCM.

Didn't change the existing probe for 'whats new' item because we're already
collecting that info.

- The same item now doesn't recreate the activity
- The app context now contains the right locale

AppCompatDelegate.setDefaultNightMode(mode). The override is necessary because the uiMode needs
to be manually updated after changing theme