Public API for statically accessing global list of window views

Android Studio's UI inspection tool needs access to the currently displayed
window(s) via publicly-accessible APIs given only a classloader -- it does
not have any activity or app Context.

Bug: 124516440
Test: atest WindowInspectorTest
Change-Id: I960165813c260ac8f8e17cc163fabf65b1417480
3 files changed