mypy

GH-143941: Move WASI-related files to Platforms/WASI #19191

Job	Run time
Run mypy on Lib/test/libregrtest	17s
Run mypy on Tools/cases_generator	19s
Run mypy on Lib/tomllib	19s
Run mypy on Tools/peg_generator	21s
Run mypy on Tools/build	16s
Run mypy on Tools/check-c-api-docs	15s
Run mypy on Lib/_pyrepl	19s
Run mypy on Tools/clinic	17s
Run mypy on Tools/jit	20s
	2m 43s

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