Export type ascription is ignored, so exports it hides stay reachable #14852

Wasmtime ignores the type ascription on component exports. For example:

(component
  (core module $m
    (func (export "f") (result i32) i32.const 1)
    (func (export "g") (result i32) i32.const 2))
  (core instance $i (instantiate $m))
  (func $f (result u32) (canon lift (core func $i "f")))
  (func $g (result u32) (canon lift (core func $i "g")))
  (instance $inst (export "f" (func $f)) (export "g" (func $g)))
  (export "hidden" (instance $inst) (instance (export "f" (func (result u32)))))
)

The ascription hides g, but component_type() still lists g under hidden, and the host can look it up with Instance::get_export_index(Some(&hidden), "g") and call it (it returns 2). Attributes that come from the ascription, such as (implements "..") or (external-id "..") on a nested export, are lost as well, and the same item can report different attributes depending on which path it's exported through.

It looks like translate.rs records (item, name) for exports and drops export.ty, and the root export types are then built from the definition rather than the ascribed type. Guests aren't affected; this is about what the embedder API exposes.