feat: allow building distro with external providers (#1967)

# What does this PR do?

We can now build a distribution that includes external providers.
Closes: https://github.com/meta-llama/llama-stack/issues/1948

## Test Plan

Build a distro with an external provider following the doc instructions.

[//]: # (## Documentation)

Added.

Rendered:


![Screenshot 2025-04-18 at 11 26
39](https://github.com/user-attachments/assets/afcf3d50-8d30-48c3-8d24-06a4b3662881)

Signed-off-by: Sébastien Han <seb@redhat.com>

tests/external-provider/llama-stack-provider-ollama/custom-distro.yaml

@@ -0,0 +1,9 @@
+version: '2'
+distribution_spec:
+  description: Custom distro for CI tests
+  providers:
+    inference:
+    - remote::custom_ollama
+image_type: container
+image_name: ci-test
+external_providers_dir: /tmp/providers.d

tests/external-provider/llama-stack-provider-ollama/custom_ollama.yaml

@@ -1,6 +1,6 @@
 adapter:
   adapter_type: custom_ollama
-  pip_packages: ["ollama", "aiohttp"]
+  pip_packages: ["ollama", "aiohttp", "tests/external-provider/llama-stack-provider-ollama"]
   config_class: llama_stack_provider_ollama.config.OllamaImplConfig
   module: llama_stack_provider_ollama
 api_dependencies: []

tests/external-provider/llama-stack-provider-ollama/run.yaml

@@ -1,14 +1,10 @@
 version: '2'
 image_name: ollama
 apis:
-- agents
-- datasetio
-- eval
 - inference
-- safety
-- scoring
 - telemetry
 - tool_runtime
+- datasetio
 - vector_io
 providers:
   inference:
@@ -24,19 +20,6 @@ providers:
         type: sqlite
         namespace: null
         db_path: ${env.SQLITE_STORE_DIR:~/.llama/distributions/ollama}/faiss_store.db
-  safety:
-  - provider_id: llama-guard
-    provider_type: inline::llama-guard
-    config:
-      excluded_categories: []
-  agents:
-  - provider_id: meta-reference
-    provider_type: inline::meta-reference
-    config:
-      persistence_store:
-        type: sqlite
-        namespace: null
-        db_path: ${env.SQLITE_STORE_DIR:~/.llama/distributions/ollama}/agents_store.db
   telemetry:
   - provider_id: meta-reference
     provider_type: inline::meta-reference
@@ -44,14 +27,6 @@ providers:
       service_name: ${env.OTEL_SERVICE_NAME:llama-stack}
       sinks: ${env.TELEMETRY_SINKS:console,sqlite}
       sqlite_db_path: ${env.SQLITE_DB_PATH:~/.llama/distributions/ollama/trace_store.db}
-  eval:
-  - provider_id: meta-reference
-    provider_type: inline::meta-reference
-    config:
-      kvstore:
-        type: sqlite
-        namespace: null
-        db_path: ${env.SQLITE_STORE_DIR:~/.llama/distributions/ollama}/meta_reference_eval.db
   datasetio:
   - provider_id: huggingface
     provider_type: remote::huggingface
@@ -67,17 +42,6 @@ providers:
         type: sqlite
         namespace: null
         db_path: ${env.SQLITE_STORE_DIR:~/.llama/distributions/ollama}/localfs_datasetio.db
-  scoring:
-  - provider_id: basic
-    provider_type: inline::basic
-    config: {}
-  - provider_id: llm-as-judge
-    provider_type: inline::llm-as-judge
-    config: {}
-  - provider_id: braintrust
-    provider_type: inline::braintrust
-    config:
-      openai_api_key: ${env.OPENAI_API_KEY:}
   tool_runtime:
   - provider_id: brave-search
     provider_type: remote::brave-search