Introduce a catch all enforcement enum to IntelligentScanVerdict

The new value SCAM_EXPERIMENT_CATCH_ALL_ENFORCEMENT will be used when
there's a scam campaign that's largely spread and we are able to track
down enforcement through pre-existing triggers. If such enforcement is
not needed but used for telemetry only, the verdict should resort to
SCAM_EXPERIMENT_CATCH_ALL instead.

Server update: cl/741258575

Bug: 406818099
Change-Id: I6c6fcce34f381bab02f19c99c03ae8fbca7e38c9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6405354
Reviewed-by: Xinghui Lu <xinghuilu@chromium.org>
Commit-Queue: Seung Jae Lim <andysjlim@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1439707}