This fixes the following timeout issue when installing PyTorch via uv.
Also see reference: https://github.com/astral-sh/uv/pull/1694,
https://github.com/astral-sh/uv/issues/1549
```
Installing pip dependencies
Using Python 3.10.16 environment at: /home/yutang/.conda/envs/distribution-myenv
× Failed to download and build `antlr4-python3-runtime==4.9.3`
├─▶ Failed to extract archive
├─▶ failed to unpack
│ `/home/yutang/.cache/uv/sdists-v7/.tmpDWX4iK/antlr4-python3-runtime-4.9.3/src/antlr4/ListTokenSource.py`
├─▶ failed to unpack
│ `antlr4-python3-runtime-4.9.3/src/antlr4/ListTokenSource.py` into
│ `/home/yutang/.cache/uv/sdists-v7/.tmpDWX4iK/antlr4-python3-runtime-4.9.3/src/antlr4/ListTokenSource.py`
├─▶ error decoding response body
├─▶ request or response body error
╰─▶ operation timed out
help: `antlr4-python3-runtime` (v4.9.3) was included because `torchtune`
(v0.5.0) depends on `omegaconf` (v2.3.0) which depends on
`antlr4-python3-runtime>=4.9.dev0, <4.10.dev0`
Failed to build target distribution-myenv with return code 1
```
---------
Signed-off-by: Yuan Tang <terrytangyuan@gmail.com>
## What does this PR do?
See issue: #747 -- `uv` is just plain better. This PR does the bare
minimum of replacing `pip install` by `uv pip install` and ensuring `uv`
exists in the environment.
## Test Plan
First: create new conda, `uv pip install -e .` on `llama-stack` -- all
is good.
Next: run `llama stack build --template together` followed by `llama
stack run together` -- all good
Next: run `llama stack build --template together --image-name yoyo`
followed by `llama stack run together --image-name yoyo` -- all good
Next: fresh conda and `uv pip install -e .` and `llama stack build
--template together --image-type venv` -- all good.
Docker: `llama stack build --template together --image-type container`
works!
