Add SystemProperty to override education prerequisite conditions

Having SystemProperty will help us override pre-conditions using adb command.
This will facilitate testing of education during PTE testing and Bugbashes.

Test: atest AppHandleEducationControllerTest
Test: atest AppHandleEducationFilterTest
Fixes: 370772025
Flag: com.android.window.flags.enable_desktop_windowing_app_handle_education
Change-Id: Ic4b246af6daa19ab36cf83ee0f793d8c5a6e49b9