armv8r64-extras/tests: Introduce basic test

Basic test cases are based on bats and include 2 categories:

- network
- SMP

The tests can be included in the build by appending 'refstack-tests'
to the build configuration's DISTRO_FEATURES.

Issue-Id: SCM-4357
Signed-off-by: Robbie Cao <robbie.cao@arm.com>
Change-Id: Ibec136d75f82833917215559dee67b7544eafb49