Update to use LLM, STT, TTS subclasses and remove setter methods

src/pipecat/frames/frames.py

@@ -530,10 +530,24 @@ class UserImageRequestFrame(ControlFrame):
 class ServiceUpdateSettingsFrame(ControlFrame):
     """A control frame containing a request to update service settings."""
 
-    service_type: str
     settings: Dict[str, Any]
 
 
+@dataclass
+class LLMUpdateSettingsFrame(ServiceUpdateSettingsFrame):
+    pass
+
+
+@dataclass
+class TTSUpdateSettingsFrame(ServiceUpdateSettingsFrame):
+    pass
+
+
+@dataclass
+class STTUpdateSettingsFrame(ServiceUpdateSettingsFrame):
+    pass
+
+
 @dataclass
 class FunctionCallInProgressFrame(SystemFrame):
     """A frame signaling that a function call is in progress."""