feat: introduce /admin API for stack administration and operations

  - Add new /admin API (v1alpha) for administrative operations including provider management, health checks, version info, and route listing
  - Implement using FastAPI routers following batches pattern with proper request/response models
  - Endpoints: /admin/providers, /admin/providers/{id}, /admin/inspect/routes, /admin/health, /admin/version
  - Create admin module structure: models.py, api.py, fastapi_routes.py, __init__.py
  - Add AdminImpl in llama_stack/core combining provider and inspect functionality
  - Deprecate standalone /providers and /inspect APIs (remain functional for backward compatibility)
  - Consolidate duplicate types: ProviderInfo, HealthInfo, RouteInfo, etc. now defined once in admin.models
  - Test new API using Stainless SDK in integration tests

Signed-off-by: Charlie Doern <[email protected]>

Author: cdoern

client-sdks/stainless/config.yml

@@ -163,6 +163,12 @@ resources:
       sampling_params: SamplingParams
       scoring_result: ScoringResult
       system_message: SystemMessage
+      health_info: HealthInfo
+      provider_info: ProviderInfo
+      list_providers_response: ListProvidersResponse
+      route_info: RouteInfo
+      list_routes_response: ListRoutesResponse
+      version_info: VersionInfo
   toolgroups:
     models:
       tool_group: ToolGroup
@@ -261,11 +267,6 @@ resources:
             type: http
             endpoint: delete /v1/conversations/{conversation_id}/items/{item_id}
   inspect:
-    models:
-      healthInfo: HealthInfo
-      providerInfo: ProviderInfo
-      routeInfo: RouteInfo
-      versionInfo: VersionInfo
     methods:
       health: get /v1/health
       version: get /v1/version
@@ -357,16 +358,12 @@ resources:
             paginated: false
             endpoint: get /v1/models
   providers:
-    models:
-      list_providers_response: ListProvidersResponse
     methods:
       list:
         paginated: false
         endpoint: get /v1/providers
       retrieve: get /v1/providers/{provider_id}
   routes:
-    models:
-      list_routes_response: ListRoutesResponse
     methods:
       list:
         paginated: false
@@ -474,6 +471,13 @@ resources:
               cancel: delete /v1alpha/eval/benchmarks/{benchmark_id}/jobs/{job_id}
               status: get /v1alpha/eval/benchmarks/{benchmark_id}/jobs/{job_id}
               retrieve: get /v1alpha/eval/benchmarks/{benchmark_id}/jobs/{job_id}/result
+      admin:
+        methods:
+          list_providers: get /v1alpha/admin/providers
+          inspect_provider: get /v1alpha/admin/providers/{provider_id}
+          list_routes: get /v1alpha/admin/inspect/routes
+          health: get /v1alpha/admin/health
+          version: get /v1alpha/admin/version
   beta:
     subresources:
       datasets: