Interface extends and type parameters extends

[kaleidawave]

• Interfaces require hoisting
• This hoisting phase can't do type parameter extensions because the pass can't reference type annotations (they might be below, thus not seen yet and in the namespace)
• Similar for extends, you can't do anything at registration, so this needs to be set later
• Modifying types (specifically the eager_fixed field on PolyNature::Generic and extends on Type::Interface) isn't great (so far managed to avoid it)
  • Maybe these need to be held separately on environment/TypeStore

[kaleidawave]

Some of this is done. Some of this requires stuff from #35. The cyclic / recursive stuff needs finishing + more tests