Add/remove the SYSTEM_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS flag into/from
SettingsHomepageActivity and SettingsPanelActivity with lifecycle.
Bug: 138442483
Test: make RunSettingsRoboTests ROBOTEST_FILTER=com.android.settings.homepage
make RunSettingsRoboTests ROBOTEST_FILTER=com.android.settings.panel
manual test
Change-Id: I72f9a947f57f74a8c09127d6c39173594c248ddc
Merged-In: I72f9a947f57f74a8c09127d6c39173594c248ddc