Closes #6724 (Allows object evaluation in devtools)

The purpose of this is to fix how objects were previously evaluated in
the developer tools.

- Before this, evaluating an object such as the `window` would `panic!`
- After this, evaluating an object such as the `window` outputs `[object
  Window]`

A few things to note:

- This commit contains `unsafe` code.
- This does not contain a test because the developer tools cannot be properly tested until #5971 lands.

components/devtools_traits/lib.rs

@@ -77,7 +77,7 @@ pub enum EvaluateJSReply {
     BooleanValue(bool),
     NumberValue(f64),
     StringValue(String),
-    ActorValue(String),
+    ActorValue { class: String, uuid: String },
 }
 
 #[derive(Deserialize, Serialize)]