rcutorture: Add RCU Tasks Trace and SRCU deadlock scenarios

Add a test number 3 that creates deadlock cycles involving one RCU
Tasks Trace step and L-1 SRCU steps.  Please note that lockdep will not
detect these deadlocks until synchronize_rcu_tasks_trace() is marked
with lockdep's new "sync" annotation, which will probably not happen
until some time after these markings prove their worth on SRCU.

Please note that these tests are available only in kernels built with
CONFIG_TASKS_TRACE_RCU=y.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>