[NXDART] Test framework architecture and bootstrap.

* Develop documented architecture for distributed runtime and build test farm.
* Use only generic portable solutions with no OS-specific hacks (i.e. Docker is Linux only).
* Target platforms: Linux, BSD, macOS, Windoze/WSL?.
* Use PyTest [1]. Each test should return PASS/FAIL result along with logs.
* Assume two configurable test areas: 1. build, 2. runtime. These should contain basic test, and should be easily extensible with extended, additional, and custom tests.
* Create easy to use bootstrap script for environment setup on end-user machines.
* Security: Consider that external malicious code or scripts can be injected by anyone as PR, and it will be executed "at premises" internal network. What mechanisms can and must be provided to avoid bad situations?

[1] https://docs.pytest.org/en/stable/