Support 8192 output tokens for Claude Sonnet 3.5 (#16358)

Release Notes:

- Added support for 8192 output tokens from Claude Sonnet 3.5
(https://x.com/alexalbert__/status/1812921642143900036)

crates/language_model/src/language_model.rs

@@ -64,6 +64,9 @@ pub trait LanguageModel: Send + Sync {
     }
 
     fn max_token_count(&self) -> usize;
+    fn max_output_tokens(&self) -> Option<u32> {
+        None
+    }
 
     fn count_tokens(
         &self,