rcutorture: Add 100-CPU configuration

The small-system rcutorture configurations have served us well for a great
many years, but it is now time to add a larger one.  This commit does
just that, but does not add it to the defaults in CFLIST.  This allows
the kvm.sh argument '--configs "4*CFLIST TREE10" to run four instances
of each of the default configurations concurrently with one instance of
the large configuration.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/testing/selftests/rcutorture/configs/rcu/TREE10

+CONFIG_SMP=y
+CONFIG_NR_CPUS=100
+CONFIG_PREEMPT_NONE=y
+CONFIG_PREEMPT_VOLUNTARY=n
+CONFIG_PREEMPT=n
+#CHECK#CONFIG_TREE_RCU=y
+CONFIG_HZ_PERIODIC=n
+CONFIG_NO_HZ_IDLE=y
+CONFIG_NO_HZ_FULL=n
+CONFIG_RCU_FAST_NO_HZ=n
+CONFIG_RCU_TRACE=n
+CONFIG_RCU_NOCB_CPU=n
+CONFIG_DEBUG_LOCK_ALLOC=n
+CONFIG_PROVE_LOCKING=n
+#CHECK#CONFIG_PROVE_RCU=n
+CONFIG_DEBUG_OBJECTS=n
+CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
+CONFIG_RCU_EXPERT=n