[scroll-anchoring] findAnchorElementRecursive should descend into subscrollers if its not maintaining a scroll anchor
<rdar://problem/116411088>
Pull request: https://github.com/WebKit/WebKit/pull/18564
Committed 272277@main (07319b820ce7): <https://commits.webkit.org/272277@main> Reviewed commits have been landed. Closing PR #18564 and removing active labels.