[Action Corner] Only subscribe to cursor position when there is pointer

device connected

Subscribing to cursor position would trigger adding input monitor for
the display. It should only be done when there is any pointer device
(e.g. mouse/touchpad) is connected to avoid unnecessary overhead.

Bug: 411091884
Test: PointerDeviceRepositoryTest
Test: ActionCornerRepositoryTest
Flag: com.android.systemui.shared.cursor_hot_corner
Change-Id: Ia98612e919555338e7f36fff676a78eb17bcc8b4