Panic when processing type aliases to owned resource handles

[kavoc-brown]

Summary

wit-bindgen panics when processing WIT files that contain type aliases to resource handles (e.g., type my-handle = own<my-resource>).

Environment

• wit-bindgen version: 0.47.0
• Affected component: wit-bindgen-core
• OS: Ubuntu 22.04, x86-64

Steps to Reproduce

1. Create a minimal WIT file

   Save the following as test.wit:

   package poc:demo;
   
   interface db {
     resource database {
       constructor();
       query: func(sql: string) -> string;
     }
   
     // Type alias to owned resource handle
     type db-handle = own<database>;
   
     connect: func() -> db-handle;
   }
   
   world test-world {
     export db;
   }

2. Run wit-bindgen

   wit-bindgen rust --out-dir /tmp/test test.wit

3. Observe the panic

   thread 'main' panicked at /home/runner/work/wit-bindgen/wit-bindgen/crates/core/src/lib.rs:183:39:
   handle types do not require definition
   note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace