Optimize FileBasedSink's WriteOperation.moveToOutput()

moveToOutput() methods in FileBasedSink.WriteOperation implements move by copy+delete. It would be better to use a rename() which can be much more effective for some filesystems.

Filesystem must support cross-directory rename. BEAM-4861 is related to this for the case of HDFS filesystem.

Feature was discussed here:

http://mail-archives.apache.org/mod_mbox/beam-dev/201807.mbox/%3CCAF9t7_4Mp54pQ+vRrJrBh9Vx0=uaKnuPZD_qdh_QDm9VXLLsZw@mail.gmail.com%3E