Update LayerUnittest to use PresentationFeedback

The current signal used is OnCompositingAckDeprecated, which we plan to
remove. This signal is also sent before drawing has occurred. So it is
not accurate, and probably a source of historical flakiness.

Here we update it to use the PresentationFeedback to know that the frame
completed the process of drawing and presenting.

Bug: 40900977
Change-Id: Idb8ac97c55d865d546cb7e2fb45befbdb35d9e46
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6828402
Reviewed-by: Saifuddin Hitawala <hitawala@chromium.org>
Auto-Submit: Jonathan Ross <jonross@chromium.org>
Commit-Queue: Jonathan Ross <jonross@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1498410}