Kwargs LiteLLM code introduces for its own use were only kept out of provider
bodies if someone also listed them in all_litellm_params. Undeclared ones went
into extra_body or optional_params, reached the provider, and the provider
rejected the request. is_litellm_owned_kwarg in types/utils.py now defines
LiteLLM-owned once: a registered name, or any name starting with
INTERNAL_KWARG_PREFIX from litellm/constants.py. Every filter that builds
provider params from kwargs uses it: chat completion, transcription,
embedding, image generation and edit, search and video, ElevenLabs text to
speech, and the Bedrock batch mapper. The two untyped shared filters now take
Mapping[str, object]
The stream_chunk_size wire test becomes test_internal_params_wire.py. It also
sends an undeclared _litellm_ kwarg and asserts that no _litellm_ key reaches
any of the six provider bodies, while extra_body passthrough keeps working
Refs LIT-8318, LIT-8319
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