[Inference Snippet] Add a directRequest option (false by default)

[Wauplin]

Fix after #1514.

Now that we use a placeholder for access token to load from env, there is no direct way to explictly generatea snippet for either a "direct request" or a "routed request" (determined here using accessToken.startsWith("hf_")). This PR adds a directRequest?: boolean; option to the parameters which solves this problem.

Will require a follow-up PR in moon-landing.

cc @SBrandeis who found out the root cause

expected behavior

display routed request by default in https://huggingface.co/deepseek-ai/DeepSeek-R1-0528?inference_api=true&inference_provider=fireworks-ai&language=sh

[Wauplin]

Thanks!