torture: Allow scenarios to be specified to torture.sh

This commit adds --configs-rcutorture, --configs-locktorture, and
--configs-scftorture arguments to torture.sh, allowing the desired
set of scenarios to be passed to each.  The default for each has been
changed from a large-system-appropriate set to just CFLIST for each.
Users are encouraged to create scripts that provide appropriate settings
for their specific systems.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>