Implement HighlightRegistry::highlightsFromPoint()

This CL implements HighlightRegistry::highlightsFromPoint().
This function is behind a feature flag HighlightsFromPoint.

See https://github.com/MicrosoftEdge/MSEdgeExplainers/blob/main/highlight/HighlightsFromPointsExplainer.md
for more details.

It also adds an extra member |registration_position| to
HighlightRegistryMapEntry to be able to break possible ties between two
Highlights with the same priority, where it's needed to check which one
was registered the latest. In this way,
before it was O(n) with n being the number of Highlights registered.
 

HighlightRegistry: :CompareOverlayStackingPosition() is now O(1), whereas
Bug: 365046212
Change-Id: I62ed3d4c404977108e291dd2cd8e1e396f351ade
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6031903
Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: Fernando Fiori <ffiori@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#1391357}