Document basic operations for V1, V2 and system cases

In the context of kata containers, I am trying to figure out how to write code that works both for legacy and unified mode. I did not find any good example of that, and I was wondering if it is documented anywhere. If not, maybe it would be nice to update the readme and other examples with code for both cases?

Also, am I correct in understanding that the module does not presently abstract away resources in the two cases, i.e. you need to use `Resources` for unified and `LinuxResources` for legacy? Is the plan that everything will switch to `Resources` over time, or will that dichotomy persist?

Assuming the two interfaces will coexist in the near future, is there any function that converts from one to the other?

(I will try to answer my own questions here, but I would appreciate if someone more knowledgeable with the project can provide some guidance, notably with respect to future intent).