HPCC-8969 - Enforce an absolute hard limit on dali results

Do not permit a dali/workunit result to exceed 2GB.
The default limit is 10MB but configurable, this new 2GB limit
is an absolute hard limit and is there to prevent misuse of
the configurable option that can result in Dali filling up with
a single rogue query result.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>