mypy

gh-127443: add tool for linting `Doc/data/refcounts.dat` #10936

Job	Run time
Run mypy on Lib/_pyrepl	24s
Run mypy on Lib/test/libregrtest	23s
Run mypy on Tools/build	23s
Run mypy on Tools/cases_generator	24s
Run mypy on Tools/clinic	22s
Run mypy on Tools/jit	23s
Run mypy on Tools/refcounts	25s
Run mypy on Tools/peg_generator	24s
Run mypy on Tools/wasm	26s
	3m 34s

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