AX: Introduce a same-origin same-site-instance non-fencedframe snapshot

This patch adds a mode to AX tree snapshotting that skips iterating
over non-same-origin or isolated frames. This is required by compose
to only gather information from same origin entries.

AX-Relnotes: n/a
R=carlosk@chromium.org, alexmos@chromium.org, yfriedman@chromium.org

Bug: 350946976
Change-Id: I890ef0740d1c0865a0f055e33f3bf0c0fb6ff131
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5718370
Reviewed-by: Carlos Knippschild <carlosk@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Commit-Queue: Vladimir Levin <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1331711}