feature request: Add set_code() API method

[antazoey]

• Version: 0.7.0b1
• Python: 3.9
• OS: macOS

What was wrong?

Looking for adding more options for set_code() to our framework and so this request is to have a way to change the contract code using eth-tester.

How can it be fixed?

    def set_code(self, address: AddressType, code: ContractCode) -> bool:
        vm = _get_vm_for_block_number(self.evm_backend.chain, "latest")
        vm.state.set_code(HexBytes(address), code)
        return True