Hiding windows for suspended packages

Suspended packages get their activities intercepted at start, but they
can still show system_alert or toast_windows from other components.
These need to be hidden when the app goes into suspend and unhidden when
it is unsuspended.

Test: atest com.android.server.wm.WindowStateTests

Bug: 77498821
Change-Id: I9ac446f20feb23e2090ba306b4435c46b9aeec95