feat: Add uv support by default

[matthewfeickert]

• By default install uv in the created virtual environment and use it to upgrade pip, setuptools, and wheel.
• Add a --no-uv option to disable this.
• Update the example in the README and examples/lcg-example.sh to use LCG 105 and el9.

* By default install uv in the created virtual environment and use
  it to upgrade pip, setuptools, and wheel.
* Add a '--no-uv' option to disable this.
* Update the example in the README and examples/lcg-example.sh to use
  LCG 105 and el9.