prototype: use pyproject and uv to build distribution

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>

.github/workflows/integration-tests.yml

@@ -41,16 +41,12 @@ jobs:
       - name: Setup ollama
         uses: ./.github/actions/setup-ollama
 
-      - name: Build Llama Stack
-        run: |
-          uv run llama stack build --template ollama --image-type venv
-
       - name: Start Llama Stack server in background
         if: matrix.client-type == 'http'
         env:
           INFERENCE_MODEL: "meta-llama/Llama-3.2-3B-Instruct"
         run: |
-          LLAMA_STACK_LOG_FILE=server.log nohup uv run llama stack run ./llama_stack/templates/ollama/run.yaml --image-type venv --env OLLAMA_URL="http://0.0.0.0:11434" &
+          LLAMA_STACK_LOG_FILE=server.log nohup uv run llama stack run ./llama_stack/templates/ollama/run.yaml --env OLLAMA_URL="http://0.0.0.0:11434"  &
 
       - name: Wait for Llama Stack server to be ready
         if: matrix.client-type == 'http'