tests

Enable mypy on CI #3995

Job	Run time
test_cygwin (39, windows-latest)	10m 47s
collateral (diffcov)	6m 17s
collateral (docs)	1m 18s
test (3.8, ubuntu-latest)	4m 26s
test (3.8, macos-latest)	8m 1s
test (3.8, windows-latest)	7m 52s
test (3.11, ubuntu-latest)	4m 3s
test (3.11, macos-latest)	5m 28s
test (3.11, windows-latest)	7m 50s
test (3.12, ubuntu-latest)	6m 14s
test (3.12, macos-latest)	7m 54s
test (3.12, windows-latest)	7m 54s
test (3.9, ubuntu-latest)	4m 30s
test (3.10, ubuntu-latest)	4m 25s
test (pypy3.10, ubuntu-latest, stdlib)	7m 48s
test (ubuntu-latest, 3.10, stdlib)	3m 54s
integration-test	0s
check	1s
release	1s
	1h 38m 43s

Provide feedback