get stack run config based on template name

[dineshyv]

This PR adds a method in stack to return the stackrunconfig object based on the template name. This will be used to instantiate a direct client without the need for an explicit run.yaml
Test plan:

1. pip install -e . on both llama stack and llama stack client with add ability to instantiate direct client with template llama-stack-client-python#37
2. Bring up ollama
3. Create a direct client:

import asyncio
from llama_stack_client.lib.direct.direct import LlamaStackDirectClient
from llama_stack.distribution.stack import (
    get_stack_run_config_from_template,
)


async def main():
    config = get_stack_run_config_from_template("ollama")
    print(f"using the following config: {config}")
    client = LlamaStackDirectClient(config)
    await client.initialize()

    response = await client.models.list()
    print(response)


if __name__ == "__main__":
    asyncio.run(main())

INFERENCE_MODEL=llama3.2:1b-instruct-fp16 python app.py

[ashwinb]

There should be a way to print out this run.yaml since the user won't know exactly what config they are starting from. DirectClient probably should dump it out when starting.