Implement pointer capture API

When in pointer capture mode, mouse pointer disappears and
further mouse events are dispatched to the focused view
in the window which has requested capture.

The captured events have the source SOURCE_MOUSE_RELATIVE
belonging to SOURCE_CLASS_TRACKBALL. They are
dispatched through dispatchCapturedPointerEvent /
onCapturedPointerEvent. There is also a new listener.

Pointer capture mode may only be granted to a currently
focused window, and will be canceled upon a window focus change.

Test: cts-tradefed ... --test android.view.cts.PointerCaptureTest
Bug: 30897034
Change-Id: I6e5934aa415ac2b6dda1cee173d0f23e5021af84