cli: restore 3.9 support via backports.entry_points_selectable
importlib.metadata.entry_points only supports the selection behavior in python 3.10+.
(This helps run swh code in a 3.9 venv, barring any other incompatibility)
Staging instance, all changes can be removed at any time
importlib.metadata.entry_points only supports the selection behavior in python 3.10+.
(This helps run swh code in a 3.9 venv, barring any other incompatibility)