mypy

gh-142598: Add new type of executable to support external JITs #20333

Job	Run time
Run mypy on Tools/cases_generator	17s
Run mypy on Tools/build	18s
Run mypy on Tools/check-c-api-docs	17s
Run mypy on Lib/test/libregrtest	17s
Run mypy on Lib/_pyrepl	16s
Run mypy on Tools/peg_generator	20s
Run mypy on Tools/jit	18s
Run mypy on Lib/tomllib	14s
Run mypy on Tools/clinic	18s
	2m 35s

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