[wayland] Implement correct release fence handling

Flatland release fences indicate when the resources of the
previous frame can be reused, not the current. Update the
commit logic to reflect this.

Bug: 84266
Change-Id: Ic195bb565f11d7981baf376ce1ea823af9fc7f92
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/585508
Commit-Queue: David Reveman <reveman@google.com>
Reviewed-by: Craig Stout <cstout@google.com>