feat(builder): add REGISTRY_PROJECT for easy registry migration

DockerHub (flat): REGISTRY_HOST=naeel, REGISTRY_PROJECT=<empty>
  -> naeel/{nsPrefix}-{func}:{tag}
Harbor/GCR (project): REGISTRY_HOST=host, REGISTRY_PROJECT=proj
  -> host/proj/{func}:{tag}

Switch registry by changing 2 env vars only.

main.go

@@ -131,9 +131,10 @@ func main() {
 	}
 
 	bldr := builder.New(mgr.GetClient(), builder.Config{
-		BuilderImage:   cfg.BuilderImage,
-		RegistryHost:   cfg.RegistryHost,
-		RegistrySecret: cfg.RegistrySecret,
+		BuilderImage:    cfg.BuilderImage,
+		RegistryHost:    cfg.RegistryHost,
+		RegistryProject: cfg.RegistryProject,
+		RegistrySecret:  cfg.RegistrySecret,
 		S3Endpoint:     cfg.S3Endpoint,
 		S3AccessKey:    cfg.S3AccessKey,
 		S3SecretKey:    cfg.S3SecretKey,