tests: kernel: mem_protect: tests for userspace mode.

The testcases presented here will test the following functionality
1. Inheritance of permission from parent thread to child.
2. Memory domain implementation.
3. Access permission for k objects.

The combinations of these test cases will cover some of the basic
usecases of the userspace mode.
These test cases are meant to be executed by any board with has
CONFIG_USERSPACE enabled.

Signed-off-by: Adithya Baglody <adithya.nagaraj.baglody@intel.com>