test: simplify pipeline

[trin94]

Hi @jaseg,

I've noticed the CI being unreliable and more annoying than helpful, so I made a few changes:

• Remove all Windows CI tests (too flaky).
• Switch to vo=null instead of vo=x11 in CI tests (more stable).
• Test only the latest stable Python (3.13) version.
• Add pytest-rerunfailures to retry failed tests (3 retries, 3s delay).
• Use uv in CI (fast, easy to use, and shiny).

Let me know if you want any changes! 😃

[jaseg]

Looks great, thank you!