Feature Request: Add Support for Contracts That Use delegatecall in the fallback Function

The simplest example that I can give is Ethernaut challenge 06 Delegate. For ease of description, I will just call them contract A and contract B. Contract A has some functions that contract B needs to be able to call which it does by delegatecall in the fallback function. As of right now, the only way to access the function in contract A through contract B is to create a function wrapper in the test contract. For this particular example, it is not a big deal as there really is only one function that needs to be wrapped. However, contract A can have an arbitrary number of functions that the user may want to fuzz.

In that case, it would be helpful if the user can identify an ABI or interface for echidna to use to call functions on contract B even though those functions are not part of its ABI.