Add only_interfaces and with to the bindgen! macro. (#6160)

* Add `only_interfaces` and `with` to the `bindgen!` macro.

* Add a version of the empty_error test for `only_interfaces` and `with`

* Review feedback

* Add docs

crates/component-macro/tests/codegen.rs

@@ -21,9 +21,17 @@ macro_rules! gentest {
                     duplicate_if_necessary: true,
                 });
             }
+            mod interfaces_only {
+                wasmtime::component::bindgen!({
+                    path: $path,
+                    world: $name,
+                    only_interfaces: true,
+                });
+            }
         }
         // ...
     };
+
 }
 
 component_macro_test_helpers::foreach!(gentest);