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/utils/inference/model_registry.py

@@ -29,7 +29,6 @@ def build_model_alias(provider_model_id: str, model_descriptor: str) -> ModelAli
     return ModelAlias(
         provider_model_id=provider_model_id,
         aliases=[
-            model_descriptor,
             get_huggingface_repo(model_descriptor),
         ],
         llama_model=model_descriptor,
@@ -57,6 +56,10 @@ class ModelRegistryHelper(ModelsProtocolPrivate):
             self.alias_to_provider_id_map[alias_obj.provider_model_id] = (
                 alias_obj.provider_model_id
             )
+            # ensure we can go from llama model to provider model id
+            self.alias_to_provider_id_map[alias_obj.llama_model] = (
+                alias_obj.provider_model_id
+            )
             self.provider_id_to_llama_model_map[alias_obj.provider_model_id] = (
                 alias_obj.llama_model
             )