fix(cloudwatch): cloudwatch ec2 alarm action with multiple dimension results in error (#29364)

### Issue # (if applicable)

Closes #29331

### Reason for this change

While trying to create a Custom Metric with multiple dimension, and adding EC2 action, the CDK synth fails.

### Description of changes

As long as there's instance id in dimension, we should accept it instead of raising exception.

### Description of how you validated changes

new tests and existing tests pass.

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

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

Author: GavinZZ

packages/aws-cdk-lib/aws-cloudwatch/lib/alarm.ts

@@ -267,7 +267,7 @@ export class Alarm extends AlarmBase {
     if (ec2ActionsRegexp.test(actionArn)) {
       // Check per-instance metric
       const metricConfig = this.metric.toMetricConfig();
-      if (metricConfig.metricStat?.dimensions?.length != 1 || metricConfig.metricStat?.dimensions![0].name != 'InstanceId') {
+      if (metricConfig.metricStat?.dimensions?.length != 1 || !metricConfig.metricStat?.dimensions?.some(dimension => dimension.name === 'InstanceId')) {
         throw new Error(`EC2 alarm actions requires an EC2 Per-Instance Metric. (${JSON.stringify(metricConfig)} does not have an 'InstanceId' dimension)`);
       }
     }

packages/aws-cdk-lib/aws-cloudwatch/test/alarm.test.ts

@@ -1,6 +1,8 @@
 import { Construct } from 'constructs';
 import { Match, Template, Annotations } from '../../assertions';
-import { Duration, Stack } from '../../core';
+import { Ec2Action, Ec2InstanceAction } from '../../aws-cloudwatch-actions/lib';
+import { Duration, Stack, App } from '../../core';
+import { ENABLE_PARTITION_LITERALS } from '../../cx-api';
 import { Alarm, IAlarm, IAlarmAction, Metric, MathExpression, IMetric, Stats } from '../lib';
 
 const testMetric = new Metric({
@@ -232,6 +234,65 @@ describe('Alarm', () => {
     });
   });
 
+  test('EC2 alarm actions with InstanceId dimension', () => {
+    // GIVEN
+    const app = new App({ context: { [ ENABLE_PARTITION_LITERALS]: true } });
+    const stack = new Stack(app, 'EC2AlarmStack', { env: { region: 'us-west-2', account: '123456789012' } });
+
+    // WHEN
+    const metric = new Metric({
+      namespace: 'CWAgent',
+      metricName: 'disk_used_percent',
+      dimensionsMap: {
+        InstanceId: 'instance-id',
+      },
+      period: Duration.minutes(5),
+      statistic: 'Average',
+    });
+
+    const sev3Alarm = new Alarm(stack, 'DISK_USED_PERCENT_SEV3', {
+      alarmName: 'DISK_USED_PERCENT_SEV3',
+      actionsEnabled: true,
+      metric: metric,
+      threshold: 1,
+      evaluationPeriods: 1,
+    });
+
+    expect(() => {
+      sev3Alarm.addAlarmAction(new Ec2Action(Ec2InstanceAction.REBOOT));
+    }).not.toThrow();
+  });
+
+  test('EC2 alarm actions without InstanceId dimension', () => {
+    // GIVEN
+    const app = new App({ context: { [ ENABLE_PARTITION_LITERALS]: true } });
+    const stack = new Stack(app, 'EC2AlarmStack', { env: { region: 'us-west-2', account: '123456789012' } });
+
+    // WHEN
+    const metric = new Metric({
+      namespace: 'CWAgent',
+      metricName: 'disk_used_percent',
+      dimensionsMap: {
+        ImageId: 'image-id',
+        InstanceType: 't2.micro',
+      },
+      period: Duration.minutes(5),
+      statistic: 'Average',
+    });
+
+    const sev3Alarm = new Alarm(stack, 'DISK_USED_PERCENT_SEV3', {
+      alarmName: 'DISK_USED_PERCENT_SEV3',
+      actionsEnabled: true,
+      metric: metric,
+      threshold: 1,
+      evaluationPeriods: 1,
+    });
+
+    expect(() => {
+      sev3Alarm.addAlarmAction(new Ec2Action(Ec2InstanceAction.REBOOT));
+    }).toThrow(/EC2 alarm actions requires an EC2 Per-Instance Metric/);
+  });
+
   test('can use percentile string to make alarm', () => {
     // GIVEN
     const stack = new Stack();