prototype: use pyproject and uv to build distribution

[leseb]

Goals:

• remove the need of a custom tool to install a collection of python packages AKA llama stack build
• use the power of 'uv', which was designed to manage dependencies
• llama stack build can "probably" go away and be replaced with uv

Howto, with the pyproject, you can install an Ollama distribution in a virtual env like so:

uv venv --python 3.10 ollama-distro
source ollama-distro/bin/activate
uv sync --extra ollama
llama stack run llama_stack/templates/ollama/run.yaml

Caveats:

• external provider, we could still use a build file or add the known external providers to the pyproject?
• growth of the uv.lock?

@ashwinb opened for discussion. I probably missed a few things but this way I think the build process will be less obscur :)