Compiler conflates object types with `Js.t` object types

Not that the object part of the compiler is very used in Melange, but there seems to be some internal coercion that is unsafe.

```ocaml
class type node = {
  pub nodeName: string;
};
let node: node = {
  "nodeName": "div",
};

Js.log(node#nodeName)
```

Crashes at runtime: `Cannot read properties of undefined (reading '0')`.