chore(ec2): add r8gb instance class

[phuhung273]

Reason for this change

https://aws.amazon.com/about-aws/whats-new/2025/09/amazon-ec2-r8gb-instances/

Description of changes

Add r8gb instance class

Description of how you validated changes

$ aws ec2 describe-instance-types \
  --filters "Name=instance-type,Values=r8gb.*" \
  --query "InstanceTypes[].InstanceType" \
  --output table
-----------------------
|DescribeInstanceTypes|
+---------------------+
|  r8gb.8xlarge       |
|  r8gb.4xlarge       |
|  r8gb.large         |
|  r8gb.12xlarge      |
|  r8gb.16xlarge      |
|  r8gb.medium        |
|  r8gb.metal-24xl    |
|  r8gb.xlarge        |
|  r8gb.2xlarge       |
|  r8gb.24xlarge      |
+---------------------+

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

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Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

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