debugger: Use JS adapter's suggested names for child sessions (#32474)

Also introduces an extension point for other adapters to do this if it
turns out they also send this information.

Release Notes:

- N/A (JS locator is still gated)

crates/dap_adapters/src/javascript.rs

@@ -431,4 +431,9 @@ impl DebugAdapter for JsDebugAdapter {
         self.get_installed_binary(delegate, &config, user_installed_path, cx)
             .await
     }
+
+    fn label_for_child_session(&self, args: &StartDebuggingRequestArguments) -> Option<String> {
+        let label = args.configuration.get("name")?.as_str()?;
+        Some(label.to_owned())
+    }
 }