mypy

gh-138122: Add --subprocesses flag to profile child processes in tach… #18526

Job	Run time
Run mypy on Lib/test/libregrtest	20s
Run mypy on Tools/clinic	16s
Run mypy on Tools/jit	21s
Run mypy on Tools/cases_generator	20s
Run mypy on Tools/peg_generator	26s
Run mypy on Lib/_pyrepl	19s
Run mypy on Tools/build	23s
Run mypy on Lib/tomllib	19s
	2m 44s

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