aws-codebuild: new images 26.03.25

### Describe the feature

https://github.com/aws/aws-codebuild-docker-images/releases/tag/26.03.25

I think the new images are these:

- standard 8.0 ([link](https://github.com/aws/aws-codebuild-docker-images/tree/master/ubuntu/standard/8.0))
- amazonlinux-x86_64-standard:6.0 ([link](https://github.com/aws/aws-codebuild-docker-images/tree/master/al/x86_64/standard/6.0))
- amazonlinux-aarch64-standard:4.0 ([link](https://github.com/aws/aws-codebuild-docker-images/tree/master/al/aarch64/standard/4.0))

Docs for image names: https://docs.aws.amazon.com/codebuild/latest/userguide/ec2-compute-images.html (note, as of writing this comment, the `amazonlinux-aarch64-standard:4.0` is missing, I think it was merged a few days after the others).

### Use Case

Use the new images in CodeBuild.

### Proposed Solution

The appropriate sub-classes of [IBuildImage](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_codebuild.IBuildImage.html) require new methods/definitions for the new images.

### Other Information

_No response_

### Acknowledgements

- [ ] I may be able to implement this feature request
- [ ] This feature might incur a breaking change

### AWS CDK Library version (aws-cdk-lib)

2.246.0

### AWS CDK CLI version

2.1115.1 (build e979d8d)

### Environment details (OS name and version, etc.)

macOS

Start with the IBuildImage interface and the linked AWS CodeBuild image documentation, then compare the three referenced image definitions with the existing CDK CodeBuild image options. Done means the appropriate subclasses expose the standard 8.0, amazonlinux-x86_64-standard:6.0, and amazonlinux-aarch64-standard:4.0 images for use in CodeBuild.

Written by the indexing model from the issue text.