Replaced 'entry_points' instances with 'backports.entry_points_selectable' one #426

Job	Run time
Static Analysis	8s
Build package	4s
Build package	13s
Call ci unit tests workflow / Run tests (3.9)	1m 45s
Call ci unit tests workflow / Run tests (3.10)	1m 43s
Call ci unit tests workflow / Run tests (3.11)	1m 43s
	5m 36s

Provide feedback