Tests

Add librt functionality for lazy deserialization #21614

Job	Run time
Test mypyc suite with 32-bit Python	10m 55s
Test suite with py314-windows-64	29m 18s
Test suite with py313-ubuntu, mypyc-compiled	16m 1s
Parallel tests with py314-ubuntu, interpreted	24m 43s
mypyc runtime tests with py313-macos	8m 32s
Type check our own code (py310-windows-64)	2m 36s
Test suite with py312-ubuntu	9m 58s
Parallel tests with py314-windows-64, interpreted	10m 5s
Test suite with py314t-ubuntu, mypyc-compiled	21m 56s
Test suite with py314-ubuntu, mypyc-compiled	15m 29s
Type check our own code (py310-ubuntu)	1m 42s
mypyc runtime tests with py310-ubuntu	6m 22s
Parallel tests with py314-ubuntu, mypyc-compiled	29m 30s
Formatting and code style with Black + ruff	1m 50s
Test suite with py311-ubuntu	9m 8s
Test suite with py310-ubuntu, mypyc-compiled	16m 26s
	3h 34m 31s

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