Update default max part size to 4GB for 32bit, and 5GB for 64bit

Issue #, if available:

• previous 32MB max part size cannot support huge files(large than 0.3TB)

Description of changes:

• Update the max part size to 4GB for 32bit, and 5GB for 64bit. The server side limit is https://docs.aws.amazon.com/AmazonS3/latest/userguide/qfacts.html.