chore: use dockerfile for building containers (#3839)

# What does this PR do?

relates to #2878 

We introduce a Containerfile which is used to replaced the `llama stack
build` command (removal in a separate PR).

```
llama stack build --distro starter --image-type venv --run
```
is replaced by
```
llama stack list-deps starter | xargs -L1 uv pip install
llama stack run starter
```


- See the updated workflow files for e2e workflow.

## Test Plan
CI
```
❯ docker build . -f docker/Dockerfile --build-arg DISTRO_NAME=starter --build-arg INSTALL_MODE=editable --tag test_starter
❯ docker run -p 8321:8321 test_starter
❯ curl http://localhost:8321/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-4o-mini",
    "messages": [
      {
        "role": "user",
        "content": "Hello!"
      }
    ]
  }'
```





---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
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[ReviewStack](https://reviewstack.dev/llamastack/llama-stack/pull/3839).
* #3855
* __->__ #3839

.github/workflows/test-external-provider-module.yml

@@ -46,9 +46,9 @@ jobs:
           yq -i '.image_type = "${{ matrix.image-type }}"' tests/external/ramalama-stack/run.yaml
           cat tests/external/ramalama-stack/run.yaml
 
-      - name: Build distro from config file
+      - name: Install distribution dependencies
         run: |
-          USE_COPY_NOT_MOUNT=true LLAMA_STACK_DIR=. uv run llama stack build --config tests/external/ramalama-stack/build.yaml
+          uv run llama stack list-deps tests/external/ramalama-stack/build.yaml | xargs -L1 uv pip install
 
       - name: Start Llama Stack server in background
         if: ${{ matrix.image-type }} == 'venv'