[CI] Use pre-built sdists for testing @ GHA rather than testing a Git checkout

[webknjaz]

Description

$sbj. One side of this is solved by my action https://github.com/re-actors/checkout-python-sdist that can replace the call to actions/checkout. Additionally, it's possible to install wheel from the built artifacts and run tests via python -Im pytest so that it doesn't hit the local dir and tests the project as installed.

Build log

No response

CI config

No response