Tests

Fix various test flakiness on Windows #21713

Job	Run time
Test mypyc suite with 32-bit Python	9m 26s
Formatting and code style with Black + ruff	1m 44s
mypyc runtime tests with py310-ubuntu	6m 53s
Parallel tests with py314-windows-64, interpreted	4m 47s
Test suite with py312-ubuntu	9m 18s
Test suite with py313-ubuntu, mypyc-compiled	9m 29s
Test suite with py314t-ubuntu, mypyc-compiled	9m 13s
Parallel tests with py314-ubuntu, interpreted	9m 29s
Test suite with py314-windows-64	9m 22s
mypyc runtime tests with py313-macos	6m 51s
Test suite with py311-ubuntu	9m 13s
Test suite with py314-ubuntu, mypyc-compiled	9m 27s
Type check our own code (py310-windows-64)	2m 34s
Test suite with py310-ubuntu, mypyc-compiled	9m 30s
Type check our own code (py310-ubuntu)	1m 44s
Parallel tests with py314-ubuntu, mypyc-compiled	9m 31s
	1h 58m 31s

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