Engine: F*: open modules providing trait impls

[W95Psp]

The PR fixes 667.

Consider the following Rust module:

mod trait_definition {
    pub trait MyTrait {
        fn my_method(self);
    }
}
mod define_type {
    pub struct MyType;
}
mod impl_type {
    impl super::trait_definition::MyTrait for super::define_type::MyType {
        fn my_method(self) {}
    }
}
mod use_type {
    fn some_function(x: super::define_type::MyType) {
        use super::trait_definition::MyTrait;
        x.my_method()
    }
}

The point here is that the type MyType, the trait MyTrait, the impl of MyTrait for MyType and the call to my_method are in four different modules.

Thus, in the module use_type, the module impl_type is never explicitly mentioned: in F* this results in the module impl_type to not be loaded at all by F*, which in turn, implies that the instance (the impl) is not in scope. Thus, the F* mechanism for resolving the instance of the typeclass MyTrait fails.

With this PR, extracting this crate, you will get the following for module use_type:

module Use_type
#set-options "--fuel 0 --ifuel 1 --z3rlimit 15"
open Core
open FStar.Mul

let _ =
  (* This module has implicit dependencies, here we make them explicit. *)
  (* The implicit dependencies arise from typeclasses instances. *)
  let open Impl_type in
  ()

let some_function (x: Define_type.t_MyType) : unit = Trait_definition.f_my_method x

[W95Psp]

This PR fails due to Kyber extraction that changes slightly: cryspen/libcrux#288