* Add Volcengine responses adapter
* fix llms/volcengine/responses/transformation.py:507:9: F841 Local variable `origin` is assigned to but never used
fix llms/volcengine/responses/transformation.py:95: error: Argument "headers" to "VolcEngineError" has incompatible type
add more supported optional params
removed redundant manual logging/utils fallbacks so litellm/__init__.py uses the registry only.
- Implemented VolcEngineEmbeddingHandler for synchronous and asynchronous embedding requests.
- Created VolcEngineEmbeddingConfig for transforming requests and responses to/from Volcengine format.
- Added integration tests for embedding functionality, covering various scenarios including error handling and parameter validation.
- Established test structure for Volcengine embedding, ensuring compliance with LiteLLM testing patterns.
- Included comprehensive tests for parameter mapping, request transformation, and response handling.