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

[phuhung273]

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

$ 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

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

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