chore(ec2): add m8a,c8i,c8i-flex instance class (#35719)

### Reason for this change
https://aws.amazon.com/about-aws/whats-new/2025/10/amazon-ec2-c8i-and-c8i-flex-instances-generally-available/
https://aws.amazon.com/about-aws/whats-new/2025/10/general-purpose-amazon-ec2-m8a-instances/

### Description of changes
EC2 add m8a,c8i,c8i-flex instance class

### Description of how you validated changes
```console
$ aws ec2 describe-instance-types \
  --filters "Name=instance-type,Values=c8i*" \      
  --query "InstanceTypes[].InstanceType" \
  --output table
-----------------------
|DescribeInstanceTypes|
+---------------------+
|  c8i-flex.8xlarge   |
|  c8i.8xlarge        |
...

$ aws ec2 describe-instance-types \
  --filters "Name=instance-type,Values=m8a.*" \     
  --query "InstanceTypes[].InstanceType" \
  --output table
-----------------------
|DescribeInstanceTypes|
+---------------------+
|  m8a.medium         |
|  m8a.8xlarge        |
...
```

### 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: phuhung273

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

@@ -750,6 +750,28 @@ export enum InstanceClass {
    */
   C7I_FLEX = 'c7i-flex',
 
+  /**
+   * Compute optimized instances based on custom Intel Xeon 6 processors, available only on AWS, 8th generation
+   */
+  COMPUTE8_INTEL = 'compute8-intel',
+
+  /**
+   * Compute optimized instances based on custom Intel Xeon 6 processors, available only on AWS, 8th generation
+   */
+  C8I = 'c8i',
+
+  /**
+   * Compute optimized instances based on custom Intel Xeon 6 processors, available only on AWS, 8th generation
+   * C8i-flex instances efficiently use compute resources to deliver a baseline level of performance with the ability to scale up to the full compute performance a majority of the time.
+   */
+  COMPUTE8_INTEL_FLEX = 'compute8-intel-flex',
+
+  /**
+   * Compute optimized instances based on custom Intel Xeon 6 processors, available only on AWS, 8th generation
+   * C8i-flex instances efficiently use compute resources to deliver a baseline level of performance with the ability to scale up to the full compute performance a majority of the time.
+   */
+  C8I_FLEX = 'c8i-flex',
+
   /**
    * Compute optimized instances based on 4th generation AMD EPYC (codename Genoa), 7th generation
    */
@@ -1445,6 +1467,16 @@ export enum InstanceClass {
    */
   M7A = 'm7a',
 
+  /**
+   * Standard instances based on 5th generation AMD EPYC (formerly code named Turin), 8th generation
+   */
+  STANDARD8_AMD = 'standard8-amd',
+
+  /**
+   * Standard instances based on 5th generation AMD EPYC (formerly code named Turin), 8th generation
+   */
+  M8A = 'm8a',
+
   /**
    * High memory and compute capacity instances, 1st generation
    */
@@ -1923,6 +1955,10 @@ export class InstanceType {
       [InstanceClass.C8GD]: 'c8gd',
       [InstanceClass.COMPUTE8_GRAVITON4_HIGH_NETWORK_BANDWIDTH]: 'c8gn',
       [InstanceClass.C8GN]: 'c8gn',
+      [InstanceClass.COMPUTE8_INTEL]: 'c8i',
+      [InstanceClass.C8I]: 'c8i',
+      [InstanceClass.COMPUTE8_INTEL_FLEX]: 'c8i-flex',
+      [InstanceClass.C8I_FLEX]: 'c8i-flex',
       [InstanceClass.STORAGE2]: 'd2',
       [InstanceClass.D2]: 'd2',
       [InstanceClass.STORAGE3]: 'd3',
@@ -2045,6 +2081,8 @@ export class InstanceType {
       [InstanceClass.M8I_FLEX]: 'm8i-flex',
       [InstanceClass.STANDARD7_AMD]: 'm7a',
       [InstanceClass.M7A]: 'm7a',
+      [InstanceClass.STANDARD8_AMD]: 'm8a',
+      [InstanceClass.M8A]: 'm8a',
       [InstanceClass.HIGH_COMPUTE_MEMORY1]: 'z1d',
       [InstanceClass.Z1D]: 'z1d',
       [InstanceClass.INFERENCE1]: 'inf1',