fix and update packaging

* drop empty setup.py which "breaks" on incomplete build envs
* use the build package to build the dist
* update the gh workflow to use it

fixup noise from pre-commit

changelog/812.feature

@@ -19,4 +19,3 @@ the fixture, the fixture was created only once.
 So restore the old behavior for typical cases where the number of tests is
 much greater than the number of workers (or, strictly speaking, when there
 are at least 2 tests for every node).
-