Common trait for companion generated structs

[mustermeiszer]

Currently, the macro bundles together multiple builders in order to generate a relay-parac-chain-setup. It would be nice if at the same point the macro could implement a trait CompanionNetwork that defines all calls the macro provides for the struct anyways.
This would allow to use the trait CompanionNetwork in function/method interfaces and increases re-usability.

The changes are rather easy.

Tasks

• [  ] Define trait in fudge primitives section
• [ ] Alter macro to implement this trait instead of exposing methods

[lemunozm]

I think this task collides with FudgeHandle from centrifuge/centrifuge-chain#1588. Ideas from FudgeHandle can be added here, and finally, remove the FudgeHandle or simplify it a lot in the centrifuge side

[lemunozm]

This task would be much easier if first we do #68