Add const generics tests for supertraits + dyn traits.

[hameerabbasi]

Partially addresses #78433

[rust-highfive]

r? @Mark-Simulacrum

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[hameerabbasi]

r? @lcnr

[lcnr]

This is already looking good, a few more cases to consider might be:

fn generic<T: Bok<N>, const N: usize>(v: T) {
    fn_taking_taking_dyn_foo::<N>(&v);
}

fn concrete<T: ?Sized + Foo<3>>(_: &T) {}
fn call_super_concrete(x: &dyn Bar<3>) {
    concrete(x);
}

Also, it would be great to change this test to // run-pass and add some simple methods to the trait and super traits and calls those too in dynamic contexts.

[lcnr]

👍

@bors r+ rollup

[bors]

📌 Commit 22060fa has been approved by lcnr