[Read Anything] Add IPH trigger.

When a web page finishes loading, if its url domain is found in the
list provided by a finch experiment, show the promo.

Implementation based on https://chromium-review.googlesource.com/c/chromium/src/+/2229149

Bug: 1266555
Change-Id: I46cc2a702fbcd60cea5db6ee45e1428afc548386
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4543896


Commit-Queue: Abigail Klein <abigailbklein@google.com>
Reviewed-by: Dana Fried <dfried@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1147615}