cfg_eval exits prematurely if it encounters an experimental_... argument

[ironcev]

cfg_eval must return false if any of the cfg attributes return false. Currently cfg_eval exists immediately if it encounters an experimental_... argument and returns the value of that particular evaluation.

E.g., in this example, the fun function exists and can be called in main, although the program_type is not a library.

script;

#[cfg(experimental_new_encoding = true)]
#[cfg(program_type = "library")]
fn fun() -> bool {
     true
}

fn main() {
    let _ = fun();
}

If the order of the two cfg attributes changes or the #[cfg(experimental_new_encoding = true)] gets removed, the cfg_eval will properly evaluate to false and the fun will not be available in main.