Tests

More testing related improvements and updates #20552

Job	Run time
Test mypyc suite with 32-bit Python	9m 31s
Test suite with py310-ubuntu, mypyc-compiled	15m 40s
mypyc runtime tests with py310-ubuntu	5m 31s
Type check our own code (py310-ubuntu)	1m 43s
Type check our own code (py310-windows-64)	2m 22s
Parallel tests with py314-ubuntu, mypyc-compiled	29m 35s
Test suite with py314-windows-64	26m 9s
Test suite with py312-ubuntu	8m 45s
Test suite with py311-ubuntu	8m 54s
Parallel tests with py314-ubuntu, interpreted	23m 37s
Test suite with py314t-ubuntu, mypyc-compiled	16m 49s
mypyc runtime tests with py313-macos	5m 28s
Test suite with py314-ubuntu, mypyc-compiled	14m 11s
Test suite with py313-ubuntu, mypyc-compiled	14m 9s
Formatting and code style with Black + ruff	1m 47s
	3h 4m 11s

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