Avoid moving visible task to front

In desktop mode, rapidly opening two apps with banners causes
the first app launched to move to the foreground and gain focus.
This occurs because the second app starts a new activity within
the same task, bringing the initial app to the front.

Bug: 399860102
Test: rapidly launch two apps
Flag: com.android.window.flags.fix_moving_unfocused_task
Change-Id: Ia4db4ff8411997d7b46f5ec220b44581c17a95b9