[Shopping UKM] Add UKM for ShoppingInformation

This CL adds UKM event to track shopping information for page load
when available.

UKM approval: https://docs.google.com/document/d/1ivwWtlYM_95mmZuW3HQ_22cIarcbiavqmrsCPKQRpXE/edit?tab=t.0

Bug: b/329869761
Change-Id: Icecd55fec84005dbb32b020451eade32bb4d963b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5389552


Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Yue Zhang <yuezhanggg@chromium.org>
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1281965}