fix(ec2): allow NAT instance to associate public IP

[GavinZZ]

Issue # (if applicable)

Closes #31711

Reason for this change

When we set mapPublicIpOnLaunch=false for public subnets, NAT instances does not get public IP addresses assigned, resulting in non-working NAT instances.

Disabling mapPublicIpOnLaunch is recommended as AWS Config rule (and cdk-nag as well.)
https://docs.aws.amazon.com/config/latest/developerguide/subnet-auto-assign-public-ip-disabled.html

Description of changes

Support associatePublicIpAddress

Description of how you validated changes

New unit and integ tests.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

---

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

[moelasmar]

I believe here you are referring to the CFN default value, but not the CDK one. I think it is better to mention that default value is null.

[moelasmar]

LGTM, left minor comment

[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).

[aws-cdk-automation]

AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: 7208988
• Result: SUCCEEDED
• Build Logs (available for 30 days)

Powered by github-codebuild-logs, available on the AWS Serverless Application Repository

[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).

[github-actions]

Comments on closed issues and PRs are hard for our team to see.
If you need help, please open a new issue that references this one.