Late initialization of the host environments

[adrien-zinger]

The problem occurs when the start function and call the ABI, it looks like the host environment isn't yet initialized and functions like
env.remaining_points.as_ref() return an error.

We can reproduce with that kind of code:

    let resolver: ImportObject = imports! {
        "my_api" => {
            // other stuff
            "foo" => Function::new_native_with_env(&store, env.clone(), foo),
        },
    };

    // [....]
    fn foo(env: &Env) {
        env.remaining_points.as_ref().unwrap() // <-- panic if foo is called in the start function
    }