TouchMode (6.1/n) Fully detaching touch mode from focus event

Note: ScreenshotTests properly exercises both IWindow#onFocusEvent and
JNI InputEventReceiver.

Bug: 193718270
Test: atest FrameworksCoreTests:ViewRootImplTest
Test: atest com.android.server.wm.ScreenshotTests
Test: atest FrameworksCoreTests
Test: atest CtsInputMethodTestCases
Test: atest CtsInputTestCases
Test: atest CtsSecurityTestCases
Test: atest CtsWindowManagerDeviceTestCases
Change-Id: I63d973978a048498e59c8df34f624b623e8e9289