[iOS] Record promo stats for trigger criteria experiment

The experiment first was design to work on older promo but now as video
promo is the new generic promo, the experiment setup should be moved to
video promo.

In this CL it record promo stats similar to what was done for the
previous version of the generic promo, deleted here
https://chromium-review.googlesource.com/c/chromium/src/+/5421030

Bug: crbug.com/326260960
Change-Id: Ie8bdcbda366376d99d7b155763093010043c157a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5617374


Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Commit-Queue: Gayane Petrosyan <gayane@google.com>
Reviewed-by: Robbie Gibson <rkgibson@google.com>
Cr-Commit-Position: refs/heads/main@{#1313181}