Add optional uv support to the Python feature

[Copilot]

The Python feature lacked support for installing uv and configuring its package indexes. This change adds optional uv installation with correct primary and extra index configuration.

• uv installation

  • Adds version and download URL options.
  • Supports AMD64/ARM64 and GNU/musl Linux archives.
  • Installs uv to /usr/local/bin.

• Index configuration

  • Writes /etc/uv/uv.toml with index-url and extra-index-url.
  • Adds override support for corporate mirrors.

• Metadata and coverage

  • Updates feature documentation and override definitions.
  • Adds an installation scenario validating uv and its configuration.

Example:

{
  "version": "system-default",
  "uvVersion": "latest",
  "uvIndexUrl": "https://pypi.org/simple",
  "uvExtraIndexUrl": "https://example.com/simple"
}

• Fixes Add support for uv in the python package #76