Stop app when toggling backcompat setting

- Add method to stop package
- Backcompat setting takes two launches right now to take effect.
stop application when backcompat setting is toggled.

Test: m Settings && adb install -r $ANDROID_PRODUCT_OUT/system_ext/priv-app/Settings/Settings.apk
Bug: 389696304
Flag: EXEMPT bug_fix
Change-Id: Iadc8030fe34f66e7eaf854513b14aeb78a556308