Add a test for an `etch` to a symbolic address

We should add the test ensuing we can `etch` to a symbolic address to the test suite:

```solidity
    function testSymbolicEtch() public {
        address etch_addr = kevm.freshAddress();
        bytes memory etch_code = bytes(hex"6060604052600436106100db576000357423dc45a92e672ff79fc00029");

        vm.etch(etch_addr, etch_code);
    }
```
