Allow exporting types directly worlds without interface

Components are also able to directly export types, so it is just a temporary WIT limitation that you're not able to define and export the math-class enum directly in the world. We should probably fix that to avoid this question.

In the meantime, you can also write:

world w {
  export types: interface {
    enum math-class { ... }
  }
}

Originally posted by @lukewagner in https://github.com/WebAssembly/component-model/issues/295#issuecomment-1904839659

The ideal is to somehow have the math-class enum on the root world instead of nested inside a redundant interface name. Unsure if you still want to pursue this.

Start by reading the WIT examples in this issue and the referenced discussion in issue 295, then review how the component model handles exported types from worlds and interfaces. The change is complete when the intended root-world type export is specified clearly and the redundant interface form is no longer required, with the desired behavior documented or covered by the project’s existing validation path.