`CallContext` should take a `Contracts` type instead of `NetworkState`

[ZER0]

Describe what you want implemented The CallContext type shouldn't depends on NetworkState, since its functionality are related only to the Contracts' state.

Describe "Why" this is needed Currently we're leaking information about which one of the multiple Contract's state the CallContext needs to operate. Although it's just internal – private to the repo – it could be confusing and a bit hard to maintain in the future: it's an unnecessary coupling.

Describe alternatives you've considered N/A

Additional context N/A

[ZER0]

Currently this issue is blocked by #304