Add assertions to CloseAppHomeButtonTest

Adding all the assertions for the CloseAppHomeButtonTest. This includes WM assertions (the common ones for all test + one that the launcher replaces the app window and another that the wallpaper window becomes visible) and layers assertions (the common ones + one for the wallpaper layer replacing the app layer).

Test: atest FlickerTests:CloseAppHomeButtonTest
Bug: b/171049778
Change-Id: I179a39914c71049002c987f5543dfa26ea6225f3