HPCC-11358 Pre-parse multivalued sort key for Total Thor Time

This fix is using Jake's code which pre-parses multivalued sort key
for Total Thor Time. WUQuery can sort WUs by Total Thor Time for
both 5.x WUs (using "Statistics/Statistic[@desc='Total thor time'
]/@value" for Total Thor Time) and 4.x WUs (using "Timings/Timing[
@name='Total thor time']/@duration" for Total Thor Time).

Signed-off-by: Kevin Wang kevin.wang@lexisnexis.com