Add handling of polymorphic constants

[clarus]

Here is an example of polymorphic constant in Rust:

fn print_array<T: std::fmt::Debug, const N: usize>(arr: [T; N]) {
    println!("{:?}", arr);
}

fn main() {
    let arr1 = [1, 2, 3];
    let arr2 = [4, 5, 6, 7, 8];

    print_array(arr1);
    print_array(arr2);

    let char_arr: [char; 3] = ['a', 'b', 'c'];
    print_array(char_arr);
}

Here, the polymorphic constant is N. In this pull request, we add such parameters with the same handling as for polymorphic types, which are also represented as values in Coq.

The aim is to be able to compile the Move Sui project that depends on such a feature to compile.

[clarus]

Fixes #496