Unify import-s grouping

Unify import-s grouping

As PEP8 (https://peps.python.org/pep-0008/) says, imports must be
grouped the following way: standard libraries, related third-party,
local application ones. "typing" is native library (since some modern
version), not third-party one.

Also, it is not explicitly noted anywhere, but imports are sorted with
ignored character case.