[PATCH v7 4/7] dts: move testbed model from framework to API

[Luca Vizzarro]

This one is a lot less ideal. For example scapy and trex provide whole 
implementations. These shouldn't live in the API package. As mentioned 
before the API package is meant to be a reliable interface to the test 
writer, so in theory only abstract functions should live there. I 
understand most of the testbed model package is indeed definitions so 
it's just a few things that need taking care of.