Tests

Treat functions that return None as returning None #19595

Job	Run time
Test mypyc suite with 32-bit Python	9m 11s
Test suite with py311-ubuntu	9m 5s
Test suite with py314-windows-64	29m 3s
Test suite with py313-ubuntu, mypyc-compiled	13m 48s
mypyc runtime tests with py310-ubuntu	5m 8s
Parallel tests with py314-ubuntu, mypyc-compiled	27m 46s
Test suite with py310-ubuntu, mypyc-compiled	14m 4s
Type check our own code (py310-ubuntu)	1m 37s
Formatting and code style with Black + ruff	1m 59s
Parallel tests with py314-ubuntu, interpreted	22m 35s
Test suite with py312-ubuntu	10m 17s
Type check our own code (py310-windows-64)	2m 29s
Test suite with py314-ubuntu, mypyc-compiled	13m 51s
mypyc runtime tests with py313-macos	6m 57s
	2h 47m 50s

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