mypy

Add documentation for Python install manager's install_dir, global_di… #17844

Job	Run time
Run mypy on Tools/cases_generator	15s
Run mypy on Tools/clinic	19s
Run mypy on Lib/test/libregrtest	18s
Run mypy on Lib/_pyrepl	19s
Run mypy on Tools/build	18s
Run mypy on Tools/peg_generator	21s
Run mypy on Lib/tomllib	19s
Run mypy on Tools/jit	19s
	2m 28s

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