Allow transfer_manager to upload/download file-like object

[shunjiad]

Is your feature request related to a problem? Please describe.
We'd like to have download_chunks_concurrently and upload_chunks_concurrently support file-like objects. That way, we can upload the model checkpoints directly from memory instead of writing them to disk first.

Describe the solution you'd like
Support passing a file-like object, such as BytesIO, to the filename in the function's argument.

Describe alternatives you've considered
Due to the lack of this functionality, I need to write my data in a local file and then upload the file to object storage.

Additional context
N/A