HPCC-10366 Add parallel query support to regression suite

Part - 1:

Add parallel query support with --pq parameter for run mode. It uses threads
to accelerate test cases execution.

Actually the result log sequence is mismatched, based on the multi-threading
and different run time of each test case.

Add 'all' parameter to query mode to run ECL program on all target clusters.

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>