Add onPointerDownOutsideFocus for events outside the focused window (1/4)

Added logic to invoke the onPointerDownOutsideFocus callback when there's an
input event that satisfies the following:
1. The event type is Motion
2. The source is pointer
3. The action is DOWN
4. The window targeted is not null
5. The window targeted is not the current focus.

Test: Builds, nothing to test yet
Bug: 122535136
Change-Id: Icae07d86dc2e2868cc594f800931220fce11942a