[Divider] Fix two bugs in interactive divider

1. Removed the isResumed() check for getting the background color. It
   cause the background color to be incorrect when secondary container
   is fully expanded and the user drags back to the split state (cannot
   get the background color of the primary container because it is
   paused at the beginning). We should rely on the signal from wm core
   to determine the trusted/untrusted state of the container instead
   (b/340239159)

2. Only the veil visibility changes should be applied in sync with the
   WCT. Other changes such as position changes should be applied
   in the app process to avoid race conditions with other local surface
   updates such as dragging.

Bug: 327067596
Test: Manual
Change-Id: Ie4406f25d133e3c6f563e5809f36744ecee142de