Tests

Fix isinstance narrowing for classes with getattr returning Any #21441

Job	Run time
Test mypyc suite with 32-bit Python	10m 20s
Test suite with py314t-ubuntu, mypyc-compiled	18m 0s
Test suite with py313-ubuntu, mypyc-compiled	15m 21s
Parallel tests with py314-ubuntu, interpreted	23m 45s
Test suite with py314-windows-64	29m 47s
Test suite with py310-ubuntu, mypyc-compiled	16m 22s
mypyc runtime tests with py313-macos	4m 46s
Test suite with py311-ubuntu	9m 59s
Type check our own code (py310-windows-64)	3m 32s
Test suite with py314-ubuntu, mypyc-compiled	16m 4s
mypyc runtime tests with py310-ubuntu	6m 25s
Parallel tests with py314-ubuntu, mypyc-compiled	25m 41s
Type check our own code (py310-ubuntu)	1m 40s
Test suite with py312-ubuntu	10m 9s
Formatting and code style with Black + ruff	1m 54s
Parallel tests with py314-windows-64, interpreted	10m 3s
	3h 23m 48s

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