Create Rust binding

[axic]

See also ETCDEVTeam/sputnikvm-ffi#12

[axic]

Ideally the API should be something like:

struct MyVM {}

impl VM for MyVM {
  fn execute(instance: &Instance, host_context: &HostContext, revision: &Revision, message: &Message, code: &[u8]) -> ExecutionResult {
  }
}

evmc_create_vm!("myvm", "1.0", MyVM)