[PWA/NavCapture] Enable clippy tests for nav capture v2/v2+supplemental

This change adds the logic for the ChromeOS experiment & tests. Getting
these to pass resulted in a number of other bugs found in the 'existing
frame' logic, and I found some extra tests that needed to be enabled for
that version that I also subsequently fixed.

Thus - the scope of this patch is slightly larger, but hopefully still
comparable.

Fixed: 396133417,396133842
Change-Id: I33c67238447a2144ce0054961920b7748f5f76e9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6308081
Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Commit-Queue: Daniel Murphy <dmurph@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1427503}