[10/n Dispatcher refactor] Move obscuring related methods to WindowInfo

In this CL we move following methods of WindowInfo subclass
1. isWindowObscured
2. isWindowObscuredAtPoint
3. findWallpaperWindowBelow

Bug: 367661487
Bug: 245989146
Test: atest inputflinger_tests
Flag: EXEMPT refactor
Change-Id: Ie7a00d485ee3a7299ce76318ad0252491606f5d0