HPCC-12677 Allow max CSV row size to be configured

The max CSV row size (default 10MB) prevents unbound CSV lines
causing problems (e.g. consuming all of memory).
10MB should be sufficient in 99% of cases, but sometimes a higher
limit is required, so allow the hard-limit to be configured via
a query #option('maxCsvRowSize', <MB>)

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Why just this one? And why the apparent replication in common/thorhelper/thorcommon.hpp