Tests

[librt] Add `librt.internal` API versioning with backward compat #19333

Job	Run time
Test mypyc suite with 32-bit Python	8m 53s
Test suite with py310-ubuntu	12m 34s
Test suite with py39-ubuntu, mypyc-compiled	7m 24s
Test suite with py311-ubuntu	9m 31s
Test suite with py313-ubuntu, mypyc-compiled	6m 15s
Test suite with py312-ubuntu, mypyc-compiled	6m 0s
Test suite with py314-ubuntu, mypyc-compiled	5m 52s
Test suite with py314-windows-64	26m 0s
Type check our own code (py39-windows-64)	2m 27s
mypyc runtime tests with py313-macos	3m 42s
Formatting and code style with Black + ruff	1m 51s
mypyc runtime tests with py310-ubuntu	4m 50s
Type check our own code (py39-ubuntu)	1m 39s
	1h 36m 58s

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