Refactor model handling and improve timeout functionality

- Removed empty string mapping from model_map in AnyModelProviderMixin.
- Updated clean_name function to exclude 'chat' from version patterns.
- Added stream_timeout parameter to AsyncGeneratorProvider for more flexible timeout handling.
- Enhanced chunk yielding in AsyncAuthedProvider to support stream_timeout, allowing for better control over asynchronous responses.

g4f/api/stubs.py

@@ -22,6 +22,7 @@ class RequestConfig(BaseModel):
     proxy: Optional[str] = None
     conversation: Optional[dict] = None
     timeout: Optional[int] = None
+    stream_timeout: Optional[int] = None
     tool_calls: list = Field(default=[], examples=[[
 		{
 			"function": {