Don't hide commands of services that are already hidden (#1438)

## Changes

Currently, the help output of services in preview doesn't show any of
their commands because the commands themselves are hidden as well.

This change updates that behavior to not hide commands in preview if the
service itself is also in preview. This makes the help output of
services in preview actually usable.

## Tests

n/a

.codegen/service.go.tmpl

@@ -39,6 +39,7 @@ import (
 
 {{define "service"}}
 {{- $excludeMethods := list "put-secret" -}}
+{{- $hideService := .IsPrivatePreview }}
 
 // Slice with functions to override default command behavior.
 // Functions can be added from the `init()` function in manually curated files in this directory.
@@ -57,7 +58,7 @@ func New() *cobra.Command {
 			"package": "{{ .Package.Name }}",
 		},
 		{{- end }}
-		{{- if .IsPrivatePreview }}
+		{{- if $hideService }}
 
 		// This service is being previewed; hide from help output.
 		Hidden: true,
@@ -190,7 +191,8 @@ func new{{.PascalName}}() *cobra.Command {
     {{- end -}}
 	`
 	{{- end }}
-	{{- if .IsPrivatePreview }}
+	{{/* Don't hide commands if the service itself is already hidden. */}}
+	{{- if and (not $hideService) .IsPrivatePreview }}
 
 	// This command is being previewed; hide from help output.
 	cmd.Hidden = true