[Supervision] Fix incorrect back navigation after PIN deletion.

Fixes a stale UI on the Supervision Dashboard after deleting a PIN. A new SupervisionListener now triggers a targeted refresh of key preferences, which correctly updates their state and visibility on the dashboard without forcing extra navigation.

Bug: 420784234
Flag: android.app.supervision.flags.enable_supervision_settings_screen
Test: atest SupervisionDeletePinPreferenceTest, atest SupervisionDashboardScreenTest
Change-Id: I871ffe4bd2727ecc12d731cd6fe0e6fae839ef6a
4 files changed