Add ASR interim results support in Assistant model and API

- Introduced `asr_interim_enabled` field in the Assistant model to control interim ASR results.
- Updated AssistantBase and AssistantUpdate schemas to include the new field.
- Modified the database schema to add the `asr_interim_enabled` column.
- Enhanced runtime metadata to reflect interim ASR settings.
- Updated API endpoints and tests to validate the new functionality.
- Adjusted documentation to include details about interim ASR results configuration.

engine/config/agents/example.yaml

@@ -44,6 +44,7 @@ agent:
     api_key: you_asr_api_key
     api_url: https://api.siliconflow.cn/v1/audio/transcriptions
     model: FunAudioLLM/SenseVoiceSmall
+    enable_interim: false
     interim_interval_ms: 500
     min_audio_ms: 300
     start_min_speech_ms: 160