feat(ec2): support for i4g instance types in aws-ec2 (#27639)

The I4g instance types were [introduced](https://aws.amazon.com/about-aws/whats-new/2023/05/amazon-ec2-i4g-storage-optimized-instances/?nc1=h_ls) in May 2023.
The instance types are supported in [CloudFormation](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-ec2-instance.html#cfn-ec2-instance-instancetype).

Closes #27631

----

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packages/aws-cdk-lib/aws-ec2/lib/instance-types.ts

@@ -596,6 +596,16 @@ export enum InstanceClass {
    */
   I4I = 'i4i',
 
+  /**
+   * Storage optimized instances powered by Graviton2 processor, 4th generation
+   */
+  STORAGE4_GRAVITON = 'storage4_graviton',
+
+  /**
+   * Storage optimized instances powered by Graviton2 processor, 4th generation
+   */
+  I4G = 'i4g',
+
   /**
    * Storage optimized instances powered by Graviton2 processor, 4th generation
    */
@@ -1291,6 +1301,8 @@ export class InstanceType {
       [InstanceClass.I3]: 'i3',
       [InstanceClass.IO3_DENSE_NVME_DRIVE]: 'i3en',
       [InstanceClass.I3EN]: 'i3en',
+      [InstanceClass.STORAGE4_GRAVITON]: 'i4g',
+      [InstanceClass.I4G]: 'i4g',
       [InstanceClass.STORAGE4_GRAVITON_NETWORK_OPTIMIZED]: 'im4gn',
       [InstanceClass.IM4GN]: 'im4gn',
       [InstanceClass.STORAGE4_GRAVITON_NETWORK_STORAGE_OPTIMIZED]: 'is4gen',