cli: prevent terraform apply drift when patching and re-applying existing terraform deployment (#1873)

The implementation would recreate the gcp instance template (including all instances and state disks) whenever the image tfvar changes.
Fixed by ignoring lifecycle changes on the instance templates.
Fixes 8c3b963

cli/internal/terraform/terraform/gcp/modules/instance_group/main.tf

@@ -16,7 +16,7 @@ locals {
 resource "google_compute_instance_template" "template" {
   name         = local.name
   machine_type = var.instance_type
-  tags         = ["constellation-${var.uid}"] // Note that this is also applied as a label 
+  tags         = ["constellation-${var.uid}"] // Note that this is also applied as a label
   labels       = merge(var.labels, { constellation-role = local.role_dashed })
 
   confidential_instance_config {
@@ -78,6 +78,19 @@ resource "google_compute_instance_template" "template" {
     enable_vtpm                 = true
     enable_integrity_monitoring = true
   }
+
+  lifecycle {
+    ignore_changes = [
+      tags,
+      labels,
+      disk, # required. update procedure modifies the instance template externally
+      metadata,
+      network_interface,
+      scheduling,
+      service_account,
+      shielded_instance_config,
+    ]
+  }
 }
 
 resource "google_compute_instance_group_manager" "instance_group_manager" {