HPCC-9595 Implement generalized paging/cache for DFU files

This fix replaces the existing paging/no cache function for
browsing logical files with new paging/cache function which
is similar to the function for browsing ECL WUs. The
MDFS_ITERATE_FILES process is enhanced to support more filters
on dali server side. A new method getLogicalFilesSorted() is
added to set/send the MDFS_ITERATE_FILES request with filters
to dali server, read the response into IPropertyTreeIterator
for sorting, and sort/cache the logical files. The old paging
code is removed from WsDFU service.

This fix also made two small changes: 1. Add ContentType for each
file to indicate a key/csv/xml/flat file; 2. Rename flag IsZipFile
to IsCompressed (keep old one for legacy);

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