Tests

[WIP] Speed up transitive_dep_hash for singleton SCCs #22079

Job	Run time
Test mypyc suite with 32-bit Python	11m 14s
Test suite with py312-ubuntu	9m 41s
Test suite with py310-ubuntu, mypyc-compiled	15m 59s
Test suite with py313-ubuntu, mypyc-compiled	15m 52s
Test suite with py314t-ubuntu, mypyc-compiled	17m 51s
Parallel tests with py314-ubuntu, interpreted	24m 23s
Test suite with py311-ubuntu	9m 7s
Parallel tests with py314-windows-64, interpreted	9m 48s
Parallel tests with py314-ubuntu, mypyc-compiled	29m 56s
Test suite with py314-windows-64	32m 1s
mypyc runtime tests with py313-macos	5m 51s
mypyc runtime tests with py310-ubuntu	6m 29s
Type check our own code (py310-ubuntu)	1m 12s
Test suite with py314-ubuntu, mypyc-compiled	15m 58s
Type check our own code (py310-windows-64)	1m 52s
Formatting and code style with Black + ruff	1m 50s
	3h 29m 4s

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