Tests

Add more test cases for type narrowing #20198

Job	Run time
Test mypyc suite with 32-bit Python	9m 29s
Test suite with py314t-ubuntu, mypyc-compiled	18m 37s
Test suite with py314-ubuntu, mypyc-compiled	15m 1s
Test suite with py311-ubuntu	9m 21s
Test suite with py314-windows-64	27m 30s
Formatting and code style with Black + ruff	1m 55s
Test suite with py310-ubuntu, mypyc-compiled	16m 0s
Parallel tests with py314-ubuntu, interpreted	22m 51s
mypyc runtime tests with py310-ubuntu	5m 39s
mypyc runtime tests with py313-macos	5m 47s
Test suite with py313-ubuntu, mypyc-compiled	14m 33s
Type check our own code (py310-windows-64)	2m 49s
Test suite with py312-ubuntu	10m 3s
Type check our own code (py310-ubuntu)	1m 50s
Parallel tests with py314-ubuntu, mypyc-compiled	27m 53s
	3h 9m 18s

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