[feature request] Support LiteLLM's Anthropic methods acreate / create for tracing

I'm using LiteLLM's Anthropic-specific methods (create() / acreate()) and these calls are not captured by the current OpenInference LiteLLM instrumentation. This means I have no observability into these calls when using Phoenix tracing. The current instrumentation only covers completion(), acompletion(), completion_with_retries(), embedding(), aembedding(), image_generation(), and aimage_generation(). Add instrumentation support for LiteLLM's Anthropic-specific methods — create() and acreate() — so that they are automatically traced and appear in Phoenix/OpenInference spans just like the other supported methods.