mypy

gh-149671: Restore compatibility with setuptools -nspkg.pth files in … #21903

Job	Run time
Run mypy on Tools/clinic	20s
Run mypy on Tools/cases_generator	19s
Run mypy on Tools/build	26s
Run mypy on Tools/check-c-api-docs	13s
Run mypy on Tools/jit	20s
Run mypy on Tools/peg_generator	20s
Run mypy on Lib/tomllib	14s
Run mypy on Lib/test/libregrtest	19s
Run mypy on Lib/_pyrepl	22s
	2m 53s

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