Tests

Fix isinstance on namedtuple type aliases #21440

Job	Run time
Test mypyc suite with 32-bit Python	9m 52s
Test suite with py311-ubuntu	10m 1s
Test suite with py314-ubuntu, mypyc-compiled	16m 2s
Type check our own code (py310-windows-64)	2m 35s
Test suite with py312-ubuntu	10m 36s
Test suite with py310-ubuntu, mypyc-compiled	17m 22s
Test suite with py313-ubuntu, mypyc-compiled	16m 9s
Type check our own code (py310-ubuntu)	1m 37s
Test suite with py314t-ubuntu, mypyc-compiled	18m 38s
mypyc runtime tests with py310-ubuntu	6m 13s
mypyc runtime tests with py313-macos	5m 15s
Parallel tests with py314-ubuntu, interpreted	24m 9s
Test suite with py314-windows-64	28m 24s
Parallel tests with py314-windows-64, interpreted	10m 47s
Formatting and code style with Black + ruff	1m 48s
Parallel tests with py314-ubuntu, mypyc-compiled	25m 55s
	3h 25m 23s

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