[NXDART] QEMU runtime tests.

* @fdcavalcanti gave us a hint to extend DRUNX with Espressif's QEMU for NuttX firmare images runtime verification with no hardware. Espressif test that way internally.
* ESP QEMU srouce code [1] https://github.com/espressif/qemu.
* All tests are Pytest [3] based, but heavily use the pytest-embedded [2] plugin, more specifically the pytest-embedded-nuttx plugin (supports Nuttshell parsing, flashing, etc).
* Espressif use docker images for testing so it cannot be intergrates into GH CI at this point directly.
* @tmedicci noticed that distributed builds can provide firmware images that can be tested in a different place on existing qemu infrastructure, so this process may be forked with build -> firmware export (A)->local runtime tests->logs (B)->external qemu testing.

[1] https://github.com/espressif/qemu
[2] https://github.com/espressif/pytest-embedded
[3] https://docs.pytest.org/en/stable/