HPCC-10183 ECL Record Layout metadata is not reported for XML files in hthor

HThor is currently not writing the ECL record layout for XML files. This
fix checks to see if that information is available and if so, writes it
along with the other file properties

Signed-off-by: William Whitehead <william.whitehead@lexisnexis.com>
Merge pull request #4948 from RussWhitehead/xmlFix

HPCC-10183 ECL Record Layout metadata is not reported for XML files in h...

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>