maint(precommit): Apply isort (#3195)

* Apply isort

* Tweak isort config

* Add env.py as a known_first_party

* Add one missing known first party

* Make config compat with older isort versions

* Add another comment

* Revert pyproject setting

tests/test_sequences_and_iterators.py

 # -*- coding: utf-8 -*-
 import pytest
-from pybind11_tests import sequences_and_iterators as m
+
 from pybind11_tests import ConstructorStats
+from pybind11_tests import sequences_and_iterators as m
 
 
 def isclose(a, b, rel_tol=1e-05, abs_tol=0.0):

tests/test_stl.py

 # -*- coding: utf-8 -*-
 import pytest
 
+from pybind11_tests import ConstructorStats, UserType
 from pybind11_tests import stl as m
-from pybind11_tests import UserType
-from pybind11_tests import ConstructorStats
 
 
 def test_vector(doc):

tests/test_stl_binders.py

@@ -2,7 +2,6 @@
 import pytest
 
 import env  # noqa: F401
-
 from pybind11_tests import stl_binders as m
 
 

tools/libsize.py

 # -*- coding: utf-8 -*-
-from __future__ import print_function, division
+from __future__ import division, print_function
+
 import os
 import sys
 

tools/make_changelog.py

@@ -4,11 +4,9 @@
 import re
 
 import ghapi.all
-
 from rich import print
 from rich.syntax import Syntax
 
-
 ENTRY = re.compile(
     r"""
     Suggested \s changelog \s entry: