torture: Indicate which torture.sh runs' bugs are all KCSAN reports

This commit further improves torture.sh run summaries by indicating
which runs' "Bugs:" counts are all KCSAN reports, and further printing
an additional end-of-run summary line when all errors reported in all
runs were KCSAN reports.

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