Tests

Bump ast-serialize to 0.4.0 #22285

Job	Run time
Test mypyc suite with 32-bit Python	11m 20s
mypyc runtime tests with py310-ubuntu	6m 59s
Test suite with py314t-ubuntu, mypyc-compiled	18m 2s
Test suite with py315-ubuntu, mypyc-compiled	15m 55s
Test suite with py310-ubuntu, mypyc-compiled	17m 16s
Test suite with py313-ubuntu, mypyc-compiled	16m 11s
Test suite with py311-ubuntu	9m 31s
Test suite with py314-ubuntu, mypyc-compiled	16m 19s
Test suite with py312-ubuntu	10m 6s
Parallel tests with py314-ubuntu, interpreted	26m 50s
Parallel tests with py314-windows-64, interpreted	10m 50s
Test suite with py314-windows-64	31m 35s
mypyc runtime tests with py313-macos	9m 28s
Type check our own code (py310-ubuntu)	1m 15s
Parallel tests with py314-ubuntu, mypyc-compiled	29m 6s
Formatting and code style with Black + ruff	1m 50s
Type check our own code (py310-windows-64)	2m 0s
	3h 54m 33s

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