Tests

Fix argparse for Python 3.14 #15492

Job	Run time
Test mypyc suite with 32-bit Python	7m 39s
Test suite with py39-ubuntu, mypyc-compiled	14m 47s
Test suite with py39-windows-64	22m 52s
Test suite with py310-ubuntu	11m 17s
Test suite with py311-ubuntu, mypyc-compiled	12m 4s
Test suite with py312-ubuntu, mypyc-compiled	14m 5s
Test suite with py313-ubuntu, mypyc-compiled	14m 29s
mypyc runtime tests with py39-macos	6m 28s
Type check our own code (py39-ubuntu)	2m 2s
Type check our own code (py39-windows-64)	2m 27s
Formatting and code style with Black + ruff	1m 44s
	1h 49m 54s

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