Use gcloud for authenticating to AR's *-docker.pkg.dev

[briandealwis]

Skaffold has special case logic to try to use GGCR's gcloud-based authenticator for gcr.io and *.gcr.io. We should also do this for *-docker.pkg.dev. This will simplify life for Cloud Deploy users. (edit: this will only affect docker builds that use the docker daemon 😢 )

skaffold/pkg/skaffold/docker/authenticators.go

Lines 100 to 105 in a3164bb

	// 3. Try gcloud for *.gcr.io
	if registry == "gcr.io" || strings.HasSuffix(registry, ".gcr.io") {
	if auth, err := google.NewGcloudAuthenticator(); err == nil {
	return auth
	}
	}

This is similar to what GGCR does already for the google keychain.

(Perhaps we can just use this google keychain?)

[renzodavid9]

Closing this, solved with:

• feat: make ADC the default option for GCP authentication when using go-containerregistry #9456
• feat: default to ADC when gcloud cred helper is configured in docker/config.json when using docker go library #9469