HPCC-9589 Introduce pseudo tables flags for xml/nlp parse

These can be used instead of the current flags in the context.  However because
of issues with hoisting table invariants currently ignoring counters the
switch from the flags can't be done yet.

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>

Next stage

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>