To valid commits once available, I integrate
current test suite into Github Actions.

Both 'udp.c' and 'unetcat.c' are tests for
UDP receiver of nstack while the code of
'udp.c' not sending anything to nstack.
So I only choose 'unetcat.c' for integration.

To test the actions, I  use 'act' (1) to
run the Gihub Actions locally in my machine,
and find out that to create network space
inside a container,the container needs to
run as privileged mode.

I use 'self-hosted' in 'runs-on' entry of jobs
related to the test suite, so I can configure
'options' entry with '--privileged'.

To simplify the task description in Github
Actions, for each test, I write a test script.