Make remaining time of timers available to LLMs (#118696)

* Include speech_slots in IntentResponse.as_dict

* Populate speech_slots only if available

* fix typo

* Add test

* test all fields

* Fix another test

---------

Co-authored-by: Paulus Schoutsen <balloob@gmail.com>

homeassistant/helpers/intent.py

@@ -1363,6 +1363,8 @@ class IntentResponse:
 
         if self.reprompt:
             response_dict["reprompt"] = self.reprompt
+        if self.speech_slots:
+            response_dict["speech_slots"] = self.speech_slots
 
         response_data: dict[str, Any] = {}