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?
We create a requirements.txt for convenience as some users are most
familiar with this format than looking at pyproject.
Signed-off-by: Sébastien Han <seb@redhat.com>
