Tests

Slightly refactor process_error_codes #20266

Job	Run time
Test mypyc suite with 32-bit Python	9m 40s
Test suite with py310-ubuntu, mypyc-compiled	15m 14s
mypyc runtime tests with py313-macos	5m 55s
Test suite with py314-windows-64	26m 37s
Test suite with py312-ubuntu	9m 51s
Test suite with py313-ubuntu, mypyc-compiled	14m 44s
Parallel tests with py314-ubuntu, mypyc-compiled	29m 6s
Type check our own code (py310-windows-64)	2m 22s
Test suite with py311-ubuntu	9m 47s
Parallel tests with py314-ubuntu, interpreted	25m 0s
Test suite with py314t-ubuntu, mypyc-compiled	17m 57s
Formatting and code style with Black + ruff	1m 56s
mypyc runtime tests with py310-ubuntu	5m 21s
Test suite with py314-ubuntu, mypyc-compiled	15m 26s
Type check our own code (py310-ubuntu)	1m 32s
	3h 10m 28s

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