Add a unit test for S3Objects

[jesusaurus]

As a first step towards gaining trust in our ability to run these lambdas with recent library versions, add a basic unit test to the S3Objects lambda to validate the functionality of resource.py

[ericzbeard]

We are archiving this repository in favor of similar content located here: https://github.com/aws-cloudformation/aws-cloudformation-templates/tree/main/aws/services/CloudFormation/MacrosExamples