mypy

Refactor `Platforms/WASI/main.py` for lazy importing and future n… #19788

Job	Run time
Run mypy on Tools/jit	16s
Run mypy on Lib/_pyrepl	18s
Run mypy on Tools/cases_generator	20s
Run mypy on Tools/check-c-api-docs	13s
Run mypy on Tools/build	20s
Run mypy on Lib/test/libregrtest	27s
Run mypy on Tools/peg_generator	21s
Run mypy on Tools/clinic	19s
Run mypy on Lib/tomllib	18s
	2m 52s

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