SyncPointerCapture (7/n): Clean up unused code from old Pointer Capture

After the pipeline changes to Pointer Capture, this CL cleans up the
following:
- The old way of notifying windows of Pointer Capture
(IWindow::dispatchPointerCaptureChanged) is removed.
- Tracking Pointer Capture in WindowManagerService is removed.

Bug: 141749603
Test: manual, flash crosshatch, pointer capture works.
Change-Id: I5bbcef42fe8d0d93a64a4a411b1d493fcb800f92