[VPAT][A11y] checkbox should have appropriate state and role announcement #173056

b/428818181

Run the https://github.com/flutter/flutter/tree/master/dev/a11y_assessments and navigate to checkboxlisttile demo

EXPECTED RESULTS:

With VoiceOver on, swipe to the "a check box list title" Custom Checkbox control.

VoiceOver announces: “a check box list title, checkbox unchecked, double tap to toggle setting" or similar.

We should double check with cloud a11y team to ensure this is indeed the correct expectation. If so, we may need to maintain the localization for these string and append them to the checkbox's label