CDK followSymlinks not supported

### SAM should support the CDK `followSymlinks` config option.

Currently SAM is the recommended tool for running CDK applications locally, as such I expect my CDK config to be compatible with SAM, however that is not always the case.
https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-cdk-testing.html

### Proposal

The CDK `followSymlinks` flag should be supported by SAM.
https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_lambda.AssetImageCodeProps.html#followsymlinks

### Additional Details

The more I think about this, I'm not even sure if this is a SAM issue, or a Cloudformation issue or a CDK issue.
Currently CDK seems to be outputting `AWS::Lambda::Function` resources, which are part of the Cloudformation spec.
I guess CDK would have to be extended to output this flag in the `Metadata` and them SAM would have to implement some logic on top?