[iOS] Use Insecure Credential Counts for Password Checkup UI Commands

This CL ensures Password Checkup UI commands triggered via the Safety
Check work reliably, even during cold starts.

Previously, these commands sometimes failed because the full list of
insecure credentials wasn't available immediately. This incorrectly sent
users to the Password Checkup homepage instead of the page for their
specific issue.

To fix this, the CL now uses the count of insecure credentials (which is
available immediately) to trigger the correct UI commands. This ensures
a consistent user experience.

Low-Coverage-Reason: TRIVIAL_CHANGE
Fixed: 365530176
Change-Id: Ie525d4988cdb45c0e478dea6cf7a88533fe7a1a7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5860478
Auto-Submit: Benjamin Williams <bwwilliams@google.com>
Commit-Queue: Benjamin Williams <bwwilliams@google.com>
Reviewed-by: Tommy Martino <tmartino@chromium.org>
Reviewed-by: Scott Yoder <scottyoder@google.com>
Cr-Commit-Position: refs/heads/main@{#1355814}