torture: Enable KCSAN summaries over groups of torture-test runs

The kcsan-collapse.sh script assumes that it is being run over the output
of a single kvm.sh run, which is less than helpful for torture.sh runs.
This commit therefore changes the kcsan-collapse.sh script's "ls" pattern
with a "find" command to enable a KCSAN summary across all the -kcsan
runs in a full torture.sh run.

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