Support sys_prompt behavior in inference (#937)

# What does this PR do?

The current default system prompt for llama3.2 tends to overindex on
tool calling and doesn't work well when the prompt does not require tool
calling.

This PR adds an option to override the default system prompt, and
organizes tool-related configs into a new config object.

- [ ] Addresses issue (#issue)


## Test Plan

python -m unittest
llama_stack.providers.tests.inference.test_prompt_adapter


## Sources

Please link relevant resources if necessary.


## Before submitting

- [ ] This PR fixes a typo or improves the docs (you can dismiss the
other checks if that's the case).
- [ ] Ran pre-commit to handle lint / formatting issues.
- [ ] Read the [contributor
guideline](https://github.com/meta-llama/llama-stack/blob/main/CONTRIBUTING.md),
      Pull Request section?
- [ ] Updated relevant documentation.
- [ ] Wrote necessary unit or integration tests.
---
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* #938
* __->__ #937

llama_stack/providers/remote/inference/nvidia/nvidia.py

@@ -171,6 +171,7 @@ class NVIDIAInferenceAdapter(Inference, ModelRegistryHelper):
         tool_prompt_format: Optional[ToolPromptFormat] = None,
         stream: Optional[bool] = False,
         logprobs: Optional[LogProbConfig] = None,
+        tool_config: Optional[ToolConfig] = None,
     ) -> Union[ChatCompletionResponse, AsyncIterator[ChatCompletionResponseStreamChunk]]:
         if tool_prompt_format:
             warnings.warn("tool_prompt_format is not supported by NVIDIA NIM, ignoring")
@@ -184,10 +185,9 @@ class NVIDIAInferenceAdapter(Inference, ModelRegistryHelper):
                 sampling_params=sampling_params,
                 response_format=response_format,
                 tools=tools,
-                tool_choice=tool_choice,
-                tool_prompt_format=tool_prompt_format,
                 stream=stream,
                 logprobs=logprobs,
+                tool_config=tool_config,
             ),
             n=1,
         )