chore: Add server side assembly of chunked blob data for RADOSGW driver

RadosGW did not support multipart copying from keys so we needed to do a local join and reupload of the whole blob. This creates issues for very big blobs where timeouts can occur. Since the issue was fixed in 2015. on the Rados side, we no longer need this part of legacy code.

See here for more information:

https://github.com/ceph/ceph/pull/5139