WICG/attribution-reporting-api#527

This CL adds aggregatable deduplication key to trigger registration to
allow deduplication mechanism for aggregatable reports. The
deduplication keys are separate for event-level and aggregatable
reports.

Bug: 1368147
Change-Id: Ic6871436e2b3a95e81d8de29f3ad58c7021d7482
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3918652
Reviewed-by: Andrew Paseltiner <apaseltiner@chromium.org>
Commit-Queue: Nan Lin <linnan@chromium.org>
Reviewed-by: John Delaney <johnidel@chromium.org>
Reviewed-by: Nate Chapin <japhet@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1052902}