Check for push permissions before building

[imjasonh]

If I'm ko publishing to a registry/repository that I don't have push permissions to (typo, misconfigured auth, incorrect active gcloud user), ko can check that and fail before building, using ggcr's CheckPushPermission.

That has a TODO(google/go-containerregistry#412) to make it unnecessary, but I think this is actually a case where it's useful, since it can avoid work and save time before remote.Writeing.

[github-actions]

This issue is stale because it has been open for 90 days with no
activity. It will automatically close after 30 more days of
inactivity. Keep fresh with the 'lifecycle/frozen' label.

[imjasonh]

I still want this.

[developer-guy]

this'd be so cool!