HPCC-10142 queryLogicalFilename not supported on hthor

Refactor the code
    - Separate the superfile processing and use nested iterators
    - Separate single file processing
    - Remove leading '~' char from logical file name.

Tested with issue10142.ecl

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>

I think there was a previous comment around here.. you don't need to test distFile, if dfIter->isValid() passed (which it has to get here) dfIter->query() must return a valid IDistributeFile, so if (distFile) not needed)