Clear app optimized mode sharedpreferences when Reset all app preferences.

- Clear events when user click Settings > Apps > All apps > top-right button > "Reset app preferences"
- Update AppOptModeSharedPreferencesUtilsTest from robotest to unit test.

Bug: 338965652
Test: atest + manual
Change-Id: Ib0a1bd113ab31fea247e5a5430ab35b252c6e1f5