tests: kernel: Stress test for round robin scheduling.

This creates 10 threads with equal priority and tests predictibility
of picking all threads in round robin fashion. Test fails when any
thread consumes more time than time slice allocated to it or threads
are not scheduled in round robin fashion.

Jira: ZEP-2371

Signed-off-by: Youvedeep Singh <youvedeep.singh@intel.com>