🚀[FEA]: Add S3 testing for filesystem abstraction

[akshaysubr]

Is this a new feature, an improvement, or a change to existing functionality?

Improvement

How would you describe the priority of this feature request

Medium

Please provide a clear description of problem you would like to solve.

Should add testing for the S3 branch of _download_cached(...)

Describe any alternatives you have considered

Shelling out to the aws cli as before but that has security risks

Additional context

Should test both with recursive=True and recursive=False