Packaging Lambda functions into a Cloud formation Template for sharing and deployment

You can use AWS Serverless Application Model to package your step-function and lambda functions - https://docs.aws.amazon.com/step-functions/latest/dg/tutorial-state-machine-using-sam.html

You could use AWS SAR if you are happy for this code to be public. Otherwise, similarly to how SAR does it, have the same template structure etc. but you then need to grant access to the bucket that stores your Lambdas code so that they can use it. Mind you, you will need to then publish the functions into buckets for each region. For example, with this template you I distribute the Lambda layer and the functions "all in one". If I wanted that to be private, the only thing for me to do is to have codebuild push to each S3 bucket (1 per region) and later on grant the access to the customers for them to pull there.