[IOS][AIM] Update and attach the tab snapshot to the page context

This CL updates the tab snapshot and attach to the page context for
better results.

Change-Id: Ibc62c0e18c900adfc24f049094eaec440950d84a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6964833
Commit-Queue: Christian Xu <christianxu@chromium.org>
Auto-Submit: Ameur Hosni <ameurhosni@google.com>
Reviewed-by: Christian Xu <christianxu@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1517159}