TouchMode (5/n) Implementing onTouchModeChanged

Changing touch mode will now have effect on every existing window
(including sys UI windows).

Manual testing steps (on gcar_emu):
1. Start emulator;
2. Ensure touch mode on by tapping anywhere in the status bar or nav
bar;
3. Tap on the launcher icon in nav bar;
4. Tap on the 3 dots in the top right corner;
5. Tap on the Close button in the dialog;
6. Rotate clockwise once to enter rotary mode. This will exit touch mode and now with this CL it will have effect on the sys UI process;
7. When tapping on home button in the nav bar, sys ui will be in touch
mode as expected.

Fixes: 173468133
Bug: 193718270
Test: manual (see steps above)
Test: atest FrameworksCoreTests:ViewRootImplTest
Change-Id: If37cd5c48087f5a25d7b8cee8fe29a5e11d9d6ae