refactor(asr): 重构speech_to_text方法以接收artifacts参数

移除各ASR提供者中重复的get_current_artifacts调用，改为通过参数传递artifacts
修改base类中process_audio方法，根据combined_pcm_data长度决定是否创建artifacts
更新所有speech_to_text方法签名，添加artifacts可选参数并更新文档字符串

main/xiaozhi-server/core/providers/asr/openai.py

@@ -24,10 +24,9 @@ class ASRProvider(ASRProviderBase):
     def requires_file(self) -> bool:
         return True
 
-    async def speech_to_text(self, opus_data: List[bytes], session_id: str, audio_format="opus") -> Tuple[Optional[str], Optional[str]]:
+    async def speech_to_text(self, opus_data: List[bytes], session_id: str, audio_format="opus", artifacts=None) -> Tuple[Optional[str], Optional[str]]:
         file_path = None
         try:
-            artifacts = self.get_current_artifacts()
             if artifacts is None:
                 return "", None
             file_path = artifacts.file_path