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. The
MDFS_ITERATE_FILTEREDFILES flag and processing code are added to
support more filters on dali server side. In ESp side, a new method
getLogicalFilesSorted() and supporting code are added to set/send
the MDFS_ITERATE_FILTEREDFILES request with filters to dali server,
read the response into IPropertyTreeIterator for sorting, and sort/
cache the logical files. The old paging code is moved into a new
method which will be called for legacy dali.

2 minor changes: (1) In dfu_search.xslt, merge the Sort Filter
FirstNType with FileSize. (2) For each file inside the response,
replace attribute IsKeyFile with ContentType.

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