script: Add message to NotFoundError (#39394)

Adding an optional message to be attached to a NotFoundError.

Testing: Just a refactor
Part of #39053

---------

Signed-off-by: Rodion Borovyk <rodion.borovyk@gmail.com>

components/script/script_module.rs

@@ -1079,7 +1079,7 @@ impl ModuleOwner {
                                 fetch_options,
                                 ScriptType::Module,
                                 global.unminified_js_dir(),
-                                Err(Error::NotFound),
+                                Err(Error::NotFound(None)),
                             )),
                         },
                     }