[view-transitions] Fix incomplete pausing of animations in reftests

Several reftests were producing off by one errors in color matching.
animation-play-state is not an inherited property from
view-transition-group(*). Where the play-state was being explicitly
paused for reftest matching, we need to explicitly pause on
image-pair, image-old and image-new as well as the group.

Flake easily reproducible with --repeat-each=10 without the patch.
Not seeing flakes with --repeat-each=100 with the patch.

Bug: 324915834
Change-Id: I76c86199f4d4734f0b2f1db0c79cdc962e2627ce
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6404354
Commit-Queue: Kevin Ellis <kevers@chromium.org>
Reviewed-by: Vladimir Levin <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1438949}