stubtest: changes for py313 (#17261) #428

Job	Run time
Test mypyc suite with 32-bit Python	7m 17s
Test suite with py38-ubuntu, mypyc-compiled	17m 5s
Test suite with py38-windows-64	19m 24s
Test suite with py39-ubuntu	16m 21s
Test suite with py310-ubuntu	15m 32s
Test suite with py311-ubuntu, mypyc-compiled	15m 15s
Test suite with py312-ubuntu, mypyc-compiled	17m 18s
mypyc runtime tests with py39-macos	4m 32s
mypyc runtime tests with py38-debug-build-ubuntu	4m 53s
Type check our own code (py38-ubuntu)	1m 46s
Type check our own code (py38-windows-64)	2m 41s
Formatting and code style with Black + ruff	41s
	2h 2m 45s

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