Skip traversal of invisible visibility change

The typical partial steps of making an existing activity visible:
1. handleAppVisibility: mAppVisible=true
2. performRestart: setWindowStopped(false)
3. performStart: Activity#makeVisible (View.VISIBLE)

A stopped activity has root view visibility=INVISIBLE. So when
changing mAppVisible to true, there will have an intermediate
GONE->INVISIBLE (host visibility is GONE if mAppVisible is false).

For root view, because it doesn't have parent, GONE and INVISIBLE
are no different. It is also the same on window manager side that
only cares about whehther it is visible or not. So the intermediate
change can be skipped to reduce overhead.

In setWindowStopped, change to use mAppVisibilityChanged to reduce
the extra invocation of destroyHardwareResources().

Bug: 205693679
Test: CtsWindowManagerDeviceTestCases
Change-Id: I16ac73e5f5b837e9946114bee73602bf8c8228a2