feat: support nvidia hosted vision models (llama 3.2 11b/90b) (#1278)

# What does this PR do?

support nvidia hosted 3.2 11b/90b vision models. they are not hosted on
the common https://integrate.api.nvidia.com/v1. they are hosted on their
own individual urls.

## Test Plan

`LLAMA_STACK_BASE_URL=http://localhost:8321 pytest -s -v
tests/client-sdk/inference/test_vision_inference.py
--inference-model=meta/llama-3.2-11b-vision-instruct -k image`

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

@@ -6,6 +6,7 @@
 
 import logging
 import warnings
+from functools import lru_cache
 from typing import AsyncIterator, List, Optional, Union
 
 from openai import APIConnectionError, AsyncOpenAI, BadRequestError
@@ -82,12 +83,42 @@ class NVIDIAInferenceAdapter(Inference, ModelRegistryHelper):
         #     )
 
         self._config = config
-        # make sure the client lives longer than any async calls
-        self._client = AsyncOpenAI(
-            base_url=f"{self._config.url}/v1",
-            api_key=(self._config.api_key.get_secret_value() if self._config.api_key else "NO KEY"),
-            timeout=self._config.timeout,
-        )
+
+    @lru_cache  # noqa: B019
+    def _get_client(self, provider_model_id: str) -> AsyncOpenAI:
+        """
+        For hosted models, https://integrate.api.nvidia.com/v1 is the primary base_url. However,
+        some models are hosted on different URLs. This function returns the appropriate client
+        for the given provider_model_id.
+
+        This relies on lru_cache and self._default_client to avoid creating a new client for each request
+        or for each model that is hosted on https://integrate.api.nvidia.com/v1.
+
+        :param provider_model_id: The provider model ID
+        :return: An OpenAI client
+        """
+
+        @lru_cache  # noqa: B019
+        def _get_client_for_base_url(base_url: str) -> AsyncOpenAI:
+            """
+            Maintain a single OpenAI client per base_url.
+            """
+            return AsyncOpenAI(
+                base_url=base_url,
+                api_key=(self._config.api_key.get_secret_value() if self._config.api_key else "NO KEY"),
+                timeout=self._config.timeout,
+            )
+
+        special_model_urls = {
+            "meta/llama-3.2-11b-vision-instruct": "https://ai.api.nvidia.com/v1/gr/meta/llama-3.2-11b-vision-instruct",
+            "meta/llama-3.2-90b-vision-instruct": "https://ai.api.nvidia.com/v1/gr/meta/llama-3.2-90b-vision-instruct",
+        }
+
+        base_url = f"{self._config.url}/v1"
+        if _is_nvidia_hosted(self._config) and provider_model_id in special_model_urls:
+            base_url = special_model_urls[provider_model_id]
+
+        return _get_client_for_base_url(base_url)
 
     async def completion(
         self,
@@ -105,9 +136,10 @@ class NVIDIAInferenceAdapter(Inference, ModelRegistryHelper):
 
         await check_health(self._config)  # this raises errors
 
+        provider_model_id = self.get_provider_model_id(model_id)
         request = convert_completion_request(
             request=CompletionRequest(
-                model=self.get_provider_model_id(model_id),
+                model=provider_model_id,
                 content=content,
                 sampling_params=sampling_params,
                 response_format=response_format,
@@ -118,7 +150,7 @@ class NVIDIAInferenceAdapter(Inference, ModelRegistryHelper):
         )
 
         try:
-            response = await self._client.completions.create(**request)
+            response = await self._get_client(provider_model_id).completions.create(**request)
         except APIConnectionError as e:
             raise ConnectionError(f"Failed to connect to NVIDIA NIM at {self._config.url}: {e}") from e
 
@@ -206,6 +238,7 @@ class NVIDIAInferenceAdapter(Inference, ModelRegistryHelper):
 
         await check_health(self._config)  # this raises errors
 
+        provider_model_id = self.get_provider_model_id(model_id)
         request = await convert_chat_completion_request(
             request=ChatCompletionRequest(
                 model=self.get_provider_model_id(model_id),
@@ -221,7 +254,7 @@ class NVIDIAInferenceAdapter(Inference, ModelRegistryHelper):
         )
 
         try:
-            response = await self._client.chat.completions.create(**request)
+            response = await self._get_client(provider_model_id).chat.completions.create(**request)
         except APIConnectionError as e:
             raise ConnectionError(f"Failed to connect to NVIDIA NIM at {self._config.url}: {e}") from e