Add Mastercard / Discover Merchant Opt Out Config + Logic

This CL adds the configuration and logic in Chrome for VCN Merchant Opt
Out for both the discover and Mastercard use-cases.

Fixed: 343558907
Change-Id: Iccffbf70ba4717a162fb5108b9d0cae2b08cdebe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5581951


Reviewed-by: Siyu An <siyua@chromium.org>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Reviewed-by: Sophie Chang <sophiechang@chromium.org>
Commit-Queue: Vinny Persky <vinnypersky@google.com>
Cr-Commit-Position: refs/heads/main@{#1313067}