s3: Add a new awss3putobjectsink
When streaming small amounts of data, using awss3sink might not be a good idea, as we need to accumulate at least 5 MB of data for a multipart upload (or we flush on EOS).
The alternative, while inefficient, is to do a complete PutObject of all the data periodically so as to not lose data in case of a pipeline failure. This element makes a start on this idea by doing a PutObject for every buffer.