tests/kernel/threads_apis: Add case for CPU_MASK_PIN_ONLY

Add testing for the PIN_ONLY API variant (which has a separate run
queue per CPU).  Predicate on SMP systems only, to keep needless
duplicate testing to a minimum.

Note that one of the cases in this test exercises an "all cpus" option
for the cpu mask, which is illegal when CONFIG_SCHED_CPU_MASK_PIN_ONLY
is set.  Skip.

Signed-off-by: Andy Ross <andrew.j.ross@intel.com>