[RFE] Cloud Credentials can be deleted even if there are clusters using them

[DovydasNavickas]

Is your feature request related to a problem? Please describe.

I had S3-Compatible Cloud Credentials and I deleted them, thinking that there will be a warning if the cluster is using them. Unfortunately, after credentials were deleted, I found this error on the cluster:

Describe the solution you'd like

When trying to delete the Cloud Credentials a warning that there is a cluster using them would be shown.

Describe alternatives you've considered

Manually checking the clusters for the credential. That maybe fine when there are only a couple of clusters, but at some point this becomes very tedious or just "delete and what breaks" kind of situation.

Additional context
Add any other context or screenshots about the feature request here.