[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: I74840ff612881cad9757707c685a20c26512d2c5