feat(server): Use system packages for execution (#1252)

# What does this PR do?

Users prefer to rely on the main CLI rather than invoking the server
through a Python module. Users interact with a high-level CLI rather
than needing to know internal module structures.

Now, when running llama stack run <path-to-config>, the server will
attempt to use the system package or a virtual environment if one is
active.

This also eliminates the current process dependency chain when running
from a virtual environment:

-> llama stack run
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; -> start_env.sh

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
-> python -m server...

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

[//]: # (If resolving an issue, uncomment and update the line below)
[//]: # (Closes #[issue-number])

## Test Plan

Run:

```
ollama run llama3.2:3b-instruct-fp16 --keepalive=2m &
llama stack run ./llama_stack/templates/ollama/run.yaml --disable-ipv6
```

Notice that the server starts and shutdowns normally.

[//]: # (## Documentation)

---------

Signed-off-by: Sébastien Han <seb@redhat.com>
Co-authored-by: Ashwin Bharambe <ashwin.bharambe@gmail.com>

llama_stack/distribution/server/server.py

@@ -17,7 +17,7 @@ import warnings
 from contextlib import asynccontextmanager
 from importlib.metadata import version as parse_version
 from pathlib import Path
-from typing import Any, List, Union
+from typing import Any, List, Optional, Union
 
 import yaml
 from fastapi import Body, FastAPI, HTTPException, Request
@@ -314,11 +314,17 @@ class ClientVersionMiddleware:
         return await self.app(scope, receive, send)
 
 
-def main():
+def main(args: Optional[argparse.Namespace] = None):
     """Start the LlamaStack server."""
     parser = argparse.ArgumentParser(description="Start the LlamaStack server.")
     parser.add_argument(
         "--yaml-config",
+        dest="config",
+        help="(Deprecated) Path to YAML configuration file - use --config instead",
+    )
+    parser.add_argument(
+        "--config",
+        dest="config",
         help="Path to YAML configuration file",
     )
     parser.add_argument(
@@ -348,7 +354,19 @@ def main():
         required="--tls-keyfile" in sys.argv,
     )
 
-    args = parser.parse_args()
+    # Determine whether the server args are being passed by the "run" command, if this is the case
+    # the args will be passed as a Namespace object to the main function, otherwise they will be
+    # parsed from the command line
+    if args is None:
+        args = parser.parse_args()
+
+    # Check for deprecated argument usage
+    if "--yaml-config" in sys.argv:
+        warnings.warn(
+            "The '--yaml-config' argument is deprecated and will be removed in a future version. Use '--config' instead.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
 
     if args.env:
         for env_pair in args.env:
@@ -360,9 +378,9 @@ def main():
                 logger.error(f"Error: {str(e)}")
                 sys.exit(1)
 
-    if args.yaml_config:
+    if args.config:
         # if the user provided a config file, use it, even if template was specified
-        config_file = Path(args.yaml_config)
+        config_file = Path(args.config)
         if not config_file.exists():
             raise ValueError(f"Config file {config_file} does not exist")
         logger.info(f"Using config file: {config_file}")