feat: add provider API for listing and inspecting provider info (#1429)

# What does this PR do?

currently the `inspect` API for providers is really a `list` API. Create
a new `providers` API which has a GET `providers/{provider_id}` inspect
API
which returns "user friendly" configuration to the end user. Also add a
GET `/providers` endpoint which returns the list of providers as
`inspect/providers` does today.

This API follows CRUD and is more intuitive/RESTful.

This work is part of the RFC at
https://github.com/meta-llama/llama-stack/pull/1359

sensitive fields are redacted using `redact_sensetive_fields` on the
server side before returning a response:

<img width="456" alt="Screenshot 2025-03-13 at 4 40 21 PM"
src="https://github.com/user-attachments/assets/9465c221-2a26-42f8-a08a-6ac4a9fecce8"
/>


## Test Plan

using https://github.com/meta-llama/llama-stack-client-python/pull/181 a
user is able to to run the following:

`llama stack build --template ollama --image-type venv`
`llama stack run --image-type venv
~/.llama/distributions/ollama/ollama-run.yaml`
`llama-stack-client providers inspect ollama`

<img width="378" alt="Screenshot 2025-03-13 at 4 39 35 PM"
src="https://github.com/user-attachments/assets/8273d05d-8bc3-44c6-9e4b-ef95e48d5466"
/>


also, was able to run the new test_list integration test locally with
ollama:

<img width="1509" alt="Screenshot 2025-03-13 at 11 03 40 AM"
src="https://github.com/user-attachments/assets/9b9db166-f02f-45b0-86a4-306d85149bc8"
/>

Signed-off-by: Charlie Doern <cdoern@redhat.com>

llama_stack/distribution/providers.py

@@ -0,0 +1,59 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+from pydantic import BaseModel
+
+from llama_stack.apis.providers import GetProviderResponse, ListProvidersResponse, ProviderInfo, Providers
+
+from .datatypes import StackRunConfig
+from .stack import redact_sensitive_fields
+
+
+class ProviderImplConfig(BaseModel):
+    run_config: StackRunConfig
+
+
+async def get_provider_impl(config, deps):
+    impl = ProviderImpl(config, deps)
+    await impl.initialize()
+    return impl
+
+
+class ProviderImpl(Providers):
+    def __init__(self, config, deps):
+        self.config = config
+        self.deps = deps
+
+    async def initialize(self) -> None:
+        pass
+
+    async def list_providers(self) -> ListProvidersResponse:
+        run_config = self.config.run_config
+        ret = []
+        for api, providers in run_config.providers.items():
+            ret.extend(
+                [
+                    ProviderInfo(
+                        api=api,
+                        provider_id=p.provider_id,
+                        provider_type=p.provider_type,
+                    )
+                    for p in providers
+                ]
+            )
+
+        return ListProvidersResponse(data=ret)
+
+    async def inspect_provider(self, provider_id: str) -> GetProviderResponse:
+        run_config = self.config.run_config
+        safe_config = StackRunConfig(**redact_sensitive_fields(run_config.model_dump()))
+        ret = None
+        for _, providers in safe_config.providers.items():
+            for p in providers:
+                if p.provider_id == provider_id:
+                    ret = p
+
+        return GetProviderResponse(data=ret)