For many tests, avoid splitting into files and put eveything in main.c.
For many of the tests, use main.c as the test source file to keep things
consistent.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
Add k_fifo kernel object usage scenario tests between thread
to thread and thread to ISR.
This test is inspired from test_fifo legacy test from
Zephyr v1.7.0 release.
Signed-off-by: Ramakrishna Pallala <ramakrishna.pallala@intel.com>