S3 Transfer Manager: bandwidth limiting for upload/download

+1 for [aws/aws-sdk-java#1103](https://github.com/aws/aws-sdk-java/issues/1103), a request for the ability to limit bandwidth for S3 uploads/downloads. See also the recently closed issue from the aws-cli repo:
https://github.com/aws/aws-cli/issues/1090

This same feature would be similarly useful in the Java SDK to help avoid fees from ISPs for excessive bandwidth usage, or to prevent a single application from overwhelming a network's capacity.

_Originally posted by @erikedlund in https://github.com/aws/aws-sdk-java-v2/issues/37#issuecomment-354880681_