Describe how to run CTS/VTS using test-definitions tradefed

[mwasilew]

android/tradefed and android/noninteractive-tradefed don't have proper documentation. This ticket is to set a reminder for improving the situation.

[daocloud123]

Any update for this?

[liuyq]

@daocloud123 could you please describe a bit on what kind of document you expect to have?