support uv

[Haoming02]

Description

• Simple Description: uv is "an extremely fast Python package and project manager, written in Rust"; it will speed up the installation process, especially during repeated installation where packages are already cached

• Summary of Changes:

1. Inside webui.bat, additionally install uv (if enabled) via pip when creating the venv
   • though, existing venv would not be updated automatically...
2. Inside launch_utils.py 's run function, replace python -m pip with uv pip if applicable to the command
3. Additionally, fall back to pip if uv failed (uv has stricter dependency rules; and not all pip flags are usable by uv)

• How to Use: add the following line to the webui-user.bat file:

set UV=1

ToDo

• Help needed for Linux / macOS port

Checklist

• I have read contributing wiki page
• I have performed a self-review of my own code
• My code follows the style guidelines
• My code passes tests