Allow hevm to define contracts with potential callbacks to execute

The feature for using `only deployed` contracts during the symbolic execution was the first step. Here is a proposal to extend it. Allow hevm to find a counter example here:

```solidity
pragma solidity ^0.8.13;

contract Counter {
uint256 public number;

function increment() public {
number++;
}
}

contract Test {
Counter c;
bool public IS_TEST = true;
function setUp() public {
c = new Counter();
}

function prove_double_increment(address t) public {
uint256 number = c.number();
Counter(t).increment();
assert(c.number() <= number + 1);
}
}
```

In this example, One external call for `increment` is not enough: hevm needs to synthesize a contract with two external calls.

The Solidity example and the existing `only deployed` contract feature are the starting points; first trace how hevm handles deployed contracts during symbolic execution. Done means hevm can synthesize multiple external calls for a potential callback and find the shown double-increment counterexample.

Written by the indexing model from the issue text.