Clear changed status of ScrollPaintPropertyNode after update

We call SetNeedsCommit for a ScrollHitTest layer if the scroll node
has changed flag set, but previously we didn't clear the flag.

Now clear changed flag from TransformPaintPropertyNodeOrAlias::
ClearChangedToRoot(). Now ClearChangedToRoot() functions are all
implemented differently in specific classes, so the generic one
is moved from PaintPropertyNode to ScrollPaintPropertyNode.

This is required by crrev.com/c/5368550.

Bug: 40256365, 40517276
Change-Id: I4f184cf2e67d8fecfdef7d60ac5acd1f8576b238
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5368587
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Reviewed-by: Stefan Zager <szager@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1273062}