add NVIDIA NIM inference adapter (#355)

# What does this PR do?

this PR adds a basic inference adapter to NVIDIA NIMs

what it does -
 - chat completion api
   - tool calls
   - streaming
   - structured output
   - logprobs
 - support hosted NIM on integrate.api.nvidia.com
 - support downloaded NIM containers

what it does not do -
 - completion api
 - embedding api
 - vision models
 - builtin tools
 - have certainty that sampling strategies are correct

## Feature/Issue validation/testing/test plan

`pytest -s -v --providers inference=nvidia
llama_stack/providers/tests/inference/ --env NVIDIA_API_KEY=...`

all tests should pass. there are pydantic v1 warnings.


## Before submitting
- [ ] This PR fixes a typo or improves the docs (you can dismiss the
other checks if that's the case).
- [x] Did you read the [contributor
guideline](https://github.com/meta-llama/llama-stack/blob/main/CONTRIBUTING.md),
      Pull Request section?
- [ ] Was this discussed/approved via a Github issue? Please add a link
      to it if that's the case.
- [ ] Did you make sure to update the documentation with your changes?
- [x] Did you write any new necessary tests?

Thanks for contributing 🎉!

llama_stack/providers/tests/inference/test_text_inference.py

@@ -198,6 +198,7 @@ class TestInference:
             "remote::fireworks",
             "remote::tgi",
             "remote::together",
+            "remote::nvidia",
         ):
             pytest.skip("Other inference providers don't support structured output yet")
 
@@ -361,7 +362,10 @@ class TestInference:
                 for chunk in grouped[ChatCompletionResponseEventType.progress]
             )
             first = grouped[ChatCompletionResponseEventType.progress][0]
-            assert first.event.delta.parse_status == ToolCallParseStatus.started
+            if not isinstance(
+                first.event.delta.content, ToolCall
+            ):  # first chunk may contain entire call
+                assert first.event.delta.parse_status == ToolCallParseStatus.started
 
         last = grouped[ChatCompletionResponseEventType.progress][-1]
         # assert last.event.stop_reason == expected_stop_reason