Fix: PyJobTransform misses logfile errors containing substep names [ATLASJT-370]

trfValidation.py, trfUtils.py, trfExe.py:
Provide an option in trfUtils such that callers can request substep
names to be removed from log lines, before parsing.
The presence of substep name 'in some log files', caused log scanner
to skip those lines since the log scaner simply looks for standard log
pattern SERVICE-LEVEL-MESSAGE.
With this update, scan behavior becomes independent of presence
(or absence) of substep names in log files.

test_trfValidation.py:
Add unit tests for log scan with Serial and MP use cases.


Former-commit-id: 9cf03f23a9801288a695764ab7e407d2bbf51319