chore: deprecate /v1/inspect/providers

[cdoern]

What does this PR do?

with the new /v1/providers API, /v1/inspect/providers is duplicative, deprecate it by removing the route, and add a test for the full /v1/providers API

resolves #1623

Test Plan

uv run pytest -v tests/integration/providers --stack-config=ollama --text-model="meta-llama/Llama-3.2-3B-Instruct" --embedding-model=all-MiniLM-L6-v2

[ashwinb]

I think llama-stack-apps (at least) has a few places where we do client.providers.list() -- should we update those callsites first?

[cdoern]

@ashwinb client.providers.list should still work I think! the v1/providers endpoint replaced v1/inspect/providers and v1/providers/provider_id is "inspect a singular provider with a config". So think leaving providers.list should be fine

[ashwinb]

client.providers.list should still work I think

could you verify this once?

[cdoern]

@ashwinb:

test_list tests client.providers.list

[cdoern]

just rebased as well to be safe!