Treat variants separately to fix their value_ptr_eq impl

[udoprog]

This fixes comparisons of variants, so that variants of the same type (same enum) don't raise a type error, but rather are simply checked for equality.

That means that code like this:

enum Foo { A, B }

pub fn main() {
    assert_eq!(Foo::A, Foo::B);
}    

Used to result in:

  ┌─ scripts\test.rn:4:5
  │
4 │     assert_eq!(Foo::A, Foo::B);
  │     ^^^^^^^^^^^^^^^^^^^^^^^^^^ unsupported vm operation `Foo::A == Foo::B`

But now instead give:

  ┌─ scripts\test.rn:4:5
  │
4 │     assert_eq!(Foo::A, Foo::B);
  │     ^^^^^^^^^^^^^^^^^^^^^^^^^^ panicked: assertion failed (left == right):
left: Foo::A
right: Foo::B

It also means that we can now successfully compare different variants of the same enum with each other without raising an error:

enum Foo { A, B }

pub fn main() {
    assert!(Foo::A != Foo::B);
}