feat(ec2): add G5 instances (#17499)

Add support for G5 instances.

Announcement: https://aws.amazon.com/about-aws/whats-new/2021/11/announcing-general-availability-amazon-ec2-g5-instances/

Add instance type `XLARGE48` which is available for G5 instances (see [EC2 Instance Types](https://aws.amazon.com/ec2/instance-types/?nc1=h_ls#Accelerated_Computing) and [CloudFormation InstanceType](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-ec2-instance.html#cfn-ec2-instance-instancetype)).

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

@@ -466,6 +466,16 @@ export enum InstanceClass {
    */
   G4DN = 'g4dn',
 
+  /**
+   * Graphics-optimized instances, 5th generation
+   */
+  GRAPHICS5 = 'g5',
+
+  /**
+   * Graphics-optimized instances, 5th generation
+   */
+  G5 = 'g5',
+
   /**
    * Parallel-processing optimized instances, 2nd generation
    */
@@ -666,6 +676,11 @@ export enum InstanceSize {
    */
   XLARGE32 = '32xlarge',
 
+  /**
+   * Instance size XLARGE48 (48xlarge)
+   */
+  XLARGE48 = '48xlarge',
+
   /**
    * Instance size METAL (metal)
    */