Wiggle: tweaks to internal interfaces (#1469)

* [wiggle]: wiggle-generate internal interface for Names simplified

im using it in other libraries where I don't want to construct a
wiggle_generate::Config just to use the ctx_type out of it.

* wiggle: define_func can get trait name as argument

this flexibility needed for some customization over in lucet

crates/wiggle/generate/src/lib.rs

@@ -15,13 +15,18 @@ pub use names::Names;
 pub use types::define_datatype;
 
 pub fn generate(doc: &witx::Document, config: &Config) -> TokenStream {
-    let names = Names::new(config); // TODO parse the names from the invocation of the macro, or from a file?
+    // TODO at some point config should grow more ability to configure name
+    // overrides.
+    let names = Names::new(&config.ctx.name);
 
     let types = doc.typenames().map(|t| define_datatype(&names, &t));
 
     let modules = doc.modules().map(|module| {
         let modname = names.module(&module.name);
-        let fs = module.funcs().map(|f| define_func(&names, &f));
+        let trait_name = names.trait_name(&module.name);
+        let fs = module
+            .funcs()
+            .map(|f| define_func(&names, &f, quote!(#trait_name)));
         let modtrait = define_module_trait(&names, &module);
         let ctx_type = names.ctx_type();
         quote!(