mypy

gh-144490: Fix test_cppext: test the internal C API (#144536) #19416

Job	Run time
Run mypy on Tools/jit	21s
Run mypy on Lib/_pyrepl	20s
Run mypy on Tools/peg_generator	18s
Run mypy on Tools/check-c-api-docs	18s
Run mypy on Tools/cases_generator	18s
Run mypy on Tools/build	26s
Run mypy on Tools/clinic	20s
Run mypy on Lib/tomllib	18s
Run mypy on Lib/test/libregrtest	19s
	2m 58s

Provide feedback