Fieldtrial config for AppsCollections HATS

Add field trial groups for Apps Collections experiment HATS survey.

AppsCollections will launch to 15% of new users for each experimental
arm. Out of all the users for AppsCollections, we need a survey to
trigger for 10% of them. And for each of those users that will be
selected for a survey, 25% will be redirected to AppsFinding vs 75%
redirected to AppsNeeding.

Assuming this calculations each group is pondered, so the sum of all 'prob' equals to .1

Bug: b:337034923
Change-Id: I6f70569c8fda03e21e6c6b0e566678aa9bb32a2f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5597801


Reviewed-by: Ian Barkley-Yeung <iby@chromium.org>
Commit-Queue: Ana Salazar <anasalazar@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1312334}