HPCC-10035 - Expose compressedSize at logical file level

Allow getDiskSize to use published meta info on compressed(disk)
part sizes and aggregate in logical file attribute in the same
way @size is currently done.

This will enable fast retreival of compressedSize possible and
expose it through DFS attribute serialization iterator routines
so that eclwatch has a cheap way to display them.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>