Fixes PB won't close sub-window of an activity as close_dialog.

Instead of check the hierarchy, check whether to close stand alone
window by it's type.

Flag: EXEMPT bugfix
Bug: 382292526
Test: atest BackNavigationControllerTests
Test: verify no matter the layer of a stand alone window is, it should
be close as TYPE_DIALOG_CLOSE.

Change-Id: Ibd4b5716aeffc37b50e61f5bf6dc26e6e20d217a