core: migrate code to benefit from 3.9 stuff

for now keeping ruff on 3.8 target version, need to sort out modules as well

my/core/utils/concurrent.py

@@ -1,6 +1,5 @@
 from __future__ import annotations
 
-import sys
 from concurrent.futures import Executor, Future
 from typing import Any, Callable, TypeVar
 

my/core/utils/imports.py

@@ -5,7 +5,6 @@ import importlib.util
 import sys
 from pathlib import Path
 from types import ModuleType
-from typing import Optional
 
 
 # TODO only used in tests? not sure if useful at all.