Track cumulative token usage in assistant2 when using anthropic API (#26738)

Release Notes:

- N/A

crates/util/src/serde.rs

@@ -1,3 +1,7 @@
 pub const fn default_true() -> bool {
     true
 }
+
+pub fn is_default<T: Default + PartialEq>(value: &T) -> bool {
+    *value == T::default()
+}