refactor(ecs): replace instanceOf into Cluster.isCluster() method (#24455)

Closes #24454 

----

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

Author: bun913

packages/@aws-cdk/aws-ecs/lib/cluster.ts

@@ -13,6 +13,8 @@ import { InstanceDrainHook } from './drain-hook/instance-drain-hook';
 import { ECSMetrics } from './ecs-canned-metrics.generated';
 import { CfnCluster, CfnCapacityProvider, CfnClusterCapacityProviderAssociations } from './ecs.generated';
 
+const CLUSTER_SYMBOL = Symbol.for('@aws-cdk/aws-ecs/lib/cluster.Cluster');
+
 /**
  * The properties used to define an ECS cluster.
  */
@@ -94,6 +96,14 @@ export enum MachineImageType {
  * A regional grouping of one or more container instances on which you can run tasks and services.
  */
 export class Cluster extends Resource implements ICluster {
+
+  /**
+    * Return whether the given object is a Cluster
+   */
+  public static isCluster(x: any) : x is Cluster {
+    return x !== null && typeof(x) === 'object' && CLUSTER_SYMBOL in x;
+  }
+
   /**
    * Import an existing cluster to the stack from its attributes.
    */
@@ -679,6 +689,12 @@ export class Cluster extends Resource implements ICluster {
   }
 }
 
+Object.defineProperty(Cluster.prototype, CLUSTER_SYMBOL, {
+  value: true,
+  enumerable: false,
+  writable: false,
+});
+
 /**
  * A regional grouping of one or more container instances on which you can run tasks and services.
  */
@@ -1259,7 +1275,7 @@ class MaybeCreateCapacityProviderAssociations implements IAspect {
   }
 
   public visit(node: IConstruct): void {
-    if (node instanceof Cluster) {
+    if (Cluster.isCluster(node)) {
       if ((this.scope.defaultCapacityProviderStrategy.length > 0 || this.scope.capacityProviderNames.length > 0 && !this.resource)) {
         this.resource = new CfnClusterCapacityProviderAssociations(this.scope, this.id, {
           cluster: node.clusterName,

packages/@aws-cdk/aws-ecs/test/cluster.test.ts

@@ -11,6 +11,38 @@ import * as cxapi from '@aws-cdk/cx-api';
 import * as ecs from '../lib';
 
 describe('cluster', () => {
+  describe('isCluster() returns', () => {
+    test('true if given cluster instance', () => {
+      // GIVEN
+      const stack = new cdk.Stack();
+      // WHEN
+      const createdCluster = new ecs.Cluster(stack, 'EcsCluster');
+      // THEN
+      expect(ecs.Cluster.isCluster(createdCluster)).toBe(true);
+    });
+
+    test('false if given imported cluster instance', () => {
+      // GIVEN
+      const stack = new cdk.Stack();
+      const vpc = new ec2.Vpc(stack, 'Vpc');
+
+      const importedSg = ec2.SecurityGroup.fromSecurityGroupId(stack, 'SG1', 'sg-1', { allowAllOutbound: false });
+      // WHEN
+      const importedCluster = ecs.Cluster.fromClusterAttributes(stack, 'Cluster', {
+        clusterName: 'cluster-name',
+        securityGroups: [importedSg],
+        vpc,
+      });
+      // THEN
+      expect(ecs.Cluster.isCluster(importedCluster)).toBe(false);
+    });
+
+    test('false if given undefined', () => {
+      // THEN
+      expect(ecs.Cluster.isCluster(undefined)).toBe(false);
+    });
+  });
+
   describe('When creating an ECS Cluster', () => {
     testDeprecated('with no properties set, it correctly sets default properties', () => {
       // GIVEN