HPCC-12213 Add new WsDFU method to retrieve meta data

A new WsDFU method DFUGetFileMetaData is added to
retrieve MetaData from DFU IResultSetMetaData.

Signed-off-by: wangkx <kevin.wang@lexisnexis.com>
I will add a comment.

The error check here informs a user the exact reason why the meta data cannot be returned if it happens. Without a dali lookup, ESP does not have the information.