Turbopack: follow-up changes from untracked tracing (#84629)

### What?

avoid some calls when tracing is not enabled

Author: sokra

turbopack/crates/turbopack-core/src/module_graph/mod.rs

@@ -1698,12 +1698,11 @@ enum SingleModuleGraphBuilderNode {
 
 impl SingleModuleGraphBuilderNode {
     async fn new_module(emit_spans: bool, module: ResolvedVc<Box<dyn Module>>) -> Result<Self> {
-        let ident = module.ident();
         Ok(Self::Module {
             module,
             ident: if emit_spans {
                 // INVALIDATION: we don't need to invalidate when the span name changes
-                Some(ident.to_string().untracked().await?)
+                Some(module.ident_string().untracked().await?)
             } else {
                 None
             },

turbopack/crates/turbopack-core/src/output.rs

@@ -20,8 +20,8 @@ pub trait OutputAsset: Asset {
     /// The identifier of the [OutputAsset] as string. It's expected to be unique and
     /// capture all properties of the [OutputAsset].
     #[turbo_tasks::function]
-    async fn path_string(self: Vc<Self>) -> Result<Vc<RcStr>> {
-        Ok(self.path().resolve().await?.to_string())
+    fn path_string(self: Vc<Self>) -> Vc<RcStr> {
+        self.path().to_string()
     }
 
     /// Other references [OutputAsset]s from this [OutputAsset].