feat: output ID of the Binary Authorization Container Analysis note

With hashicorp/terraform-provider-google#7745 soon to be added, users
will now be able to complete the full Binary Authorization multi-project
flow via Terraform.

modules/binary-authorization/outputs.tf

@@ -23,3 +23,8 @@ output "attestor" {
   value       = google_binary_authorization_attestor.attestor.name
   description = "Name of the built attestor"
 }
+
+output "note_id" {
+  value       = google_container_analysis_note.build-note.id
+  description = "ID of the created Container Analysis note"
+}