[anchor-position] Support anchor-scroll with relpos inline containers

This is a follow-up patch of crrev.com/c/4546546 to properly support
anchor-scroll on relatively positioned inline containers. Instead of
the ContainingBlock(), this patch uses NGInlineCursor to go through
the box fragments of the inline container and look for already built
NGPhysicalAnchorQuery objects there.

Fixed: 1446442
Change-Id: Ia8c9ef01d8bff8ccd70b5ba62c21cf4b981acb41
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4553048


Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1148021}