[Metadata][Metrics] Do not log issuer specific metrics for cloud token metadata

Currently cards that have an issuer id, but are not part of the issuer
integration will log histogram like
"Autofill.CreditCard..ShownWithMetadata" with an empty issuer id.

Issuer id is not tied to metadata, so we should not rely on it to log
metrics. For the metadata project, we're interested in issuer metrics
for only issuers that have direct integration.

It is possible that cards that get metadata from network integration
(cloud token metadata) also have an issuer id. Do not log issuer metrics
for such cards.

Bug: 1464789
Change-Id: I27f86af65eff05f61c5b4049afc20f0c8f3c9594
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4684035


Commit-Queue: Vishwas Uppoor <vishwasuppoor@google.com>
Code-Coverage: Findit <findit-for-me@appspot.gserviceaccount.com>
Reviewed-by: Siyu An <siyua@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1171405}