feat: Expose AWS endpointOverride option

[jecaro]

This allows you to connect to a local minio server. This is based on this idea.

It adds a new option endpoint_override which is given to the S3 client. I wrapped it up in a new struct AwsOptions like in the original idea as it opens the door to additional useful settings such as proxy, scheme, etc... Let me know if you want me to add some of them as part of this PR.

As for me, this is good enough to connect to a local minio server:

• I set the bucket prefix to "" (It currently defaults to "rockset." and AWS will try to resolve the bucket name as a domain in this case)
• I set endpoint_override to "http://127.0.0.1:9000"