Economic protocol scenario 3 - contract earns fees

[miloszm]

Summary

We have a mechanism for "contract-pays-for-gas" scenario, now, based on similar approach we need to implement "contract-earns-fees" scenario.

Possible solution design or implementation

Make a method named "set_charge" available for contracts, and pass the charge down to the transfer contract. Transfer contract will increase contract's balance and pass down the signal for increasing the fee. Should the fee be not paid, the transaction will be rejected.

Additional context

This issue is related to Rusk issue 1630