Implement DashScope ASR provider and enhance ASR service architecture

- Added DashScope ASR service implementation for real-time streaming.
- Updated ASR provider logic to support DashScope alongside existing providers.
- Enhanced runtime metadata resolution to include DashScope as a valid ASR provider.
- Modified configuration files and documentation to reflect the addition of DashScope.
- Introduced tests to validate DashScope integration and ASR service behavior.
- Refactored ASR service factory to accommodate new provider options and modes.

engine/tests/test_tool_call_flow.py

@@ -52,9 +52,33 @@ class _FakeTTS:
 
 
 class _FakeASR:
+    mode = "offline"
+
     async def connect(self) -> None:
         return None
 
+    async def disconnect(self) -> None:
+        return None
+
+    async def send_audio(self, _audio: bytes) -> None:
+        return None
+
+    async def receive_transcripts(self):
+        if False:
+            yield None
+
+    def clear_buffer(self) -> None:
+        return None
+
+    async def start_interim_transcription(self) -> None:
+        return None
+
+    async def stop_interim_transcription(self) -> None:
+        return None
+
+    async def get_final_transcription(self) -> str:
+        return ""
+
 
 class _FakeLLM:
     def __init__(self, rounds: List[List[LLMStreamEvent]]):