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/stack.py

@@ -23,6 +23,7 @@ from llama_stack.apis.inference import Inference
 from llama_stack.apis.inspect import Inspect
 from llama_stack.apis.models import Models
 from llama_stack.apis.post_training import PostTraining
+from llama_stack.apis.providers import Providers
 from llama_stack.apis.safety import Safety
 from llama_stack.apis.scoring import Scoring
 from llama_stack.apis.scoring_functions import ScoringFunctions
@@ -44,6 +45,7 @@ logger = get_logger(name=__name__, category="core")
 
 
 class LlamaStack(
+    Providers,
     VectorDBs,
     Inference,
     BatchInference,