torture: Allow --kconfig options to override --kcsan defaults

Currently, attempting to override a --kcsan default with a --kconfig
option might or might not work.  However, it would be good to allow the
user to adjust the --kcsan defaults, for example, to specify a different
time for CONFIG_KCSAN_REPORT_ONCE_IN_MS.  This commit therefore uses the
new config_override_param() bash function to apply the --kcsan defaults
and then apply the --kconfig options, which allows this overriding
to occur.

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