chore(eks): remove propertyOverride for nodegroup launchTemplate (#14499

)

Previously we use `addPropertyOverride()` when specifying launch template for a nodegroup:
https://github.com/aws/aws-cdk/blob/e11d5378c33bea609ed09c998b305fdfd28999a9/packages/%40aws-cdk/aws-eks/lib/managed-nodegroup.ts#L359-L363

This is now available on new cfn spec that cdk uses. So we can safely migrate to cfn props instead of calling `addPropertyOverride()`.

The unit test should still covered the changes:
https://github.com/aws/aws-cdk/blob/e11d5378c33bea609ed09c998b305fdfd28999a9/packages/%40aws-cdk/aws-eks/test/test.nodegroup.ts#L565-L643

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/aws-eks/lib/managed-nodegroup.ts

@@ -280,6 +280,12 @@ export class Nodegroup extends Resource implements INodegroup {
       throw new Error(`Minimum capacity ${this.minSize} can't be greater than desired size ${this.desiredSize}`);
     }
 
+    if (props.launchTemplateSpec && props.diskSize) {
+      // see - https://docs.aws.amazon.com/eks/latest/userguide/launch-templates.html
+      // and https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-eks-nodegroup.html#cfn-eks-nodegroup-disksize
+      throw new Error('diskSize must be specified within the launch template');
+    }
+
     if (props.instanceType && props.instanceTypes) {
       throw new Error('"instanceType is deprecated, please use "instanceTypes" only.');
     }
@@ -331,6 +337,7 @@ export class Nodegroup extends Resource implements INodegroup {
       // because this doesn't have a default value, meaning the user had to explicitly configure this.
       instanceTypes: instanceTypes?.map(t => t.toString()),
       labels: props.labels,
+      launchTemplate: props.launchTemplateSpec,
       releaseVersion: props.releaseVersion,
       remoteAccess: props.remoteAccess ? {
         ec2SshKey: props.remoteAccess.sshKeyName,
@@ -345,25 +352,6 @@ export class Nodegroup extends Resource implements INodegroup {
       tags: props.tags,
     });
 
-    if (props.launchTemplateSpec) {
-      if (props.diskSize) {
-        // see - https://docs.aws.amazon.com/eks/latest/userguide/launch-templates.html
-        // and https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-eks-nodegroup.html#cfn-eks-nodegroup-disksize
-        throw new Error('diskSize must be specified within the launch template');
-      }
-      /**
-       * Instance types can be specified either in `instanceType` or launch template but not both. AS we can not check the content of
-       * the provided launch template and the `instanceType` property is preferrable. We allow users to define `instanceType` property here.
-       * see - https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-eks-nodegroup.html#cfn-eks-nodegroup-instancetypes
-       */
-      // TODO: update this when the L1 resource spec is updated.
-      resource.addPropertyOverride('LaunchTemplate', {
-        Id: props.launchTemplateSpec.id,
-        Version: props.launchTemplateSpec.version,
-      });
-    }
-
-
     // managed nodegroups update the `aws-auth` on creation, but we still need to track
     // its state for consistency.
     if (this.cluster instanceof Cluster) {