Tests

Migrate extension-cpp to stable API/ABI #62

Job	Run time
unittests-linux (3.11, linux.12xlarge, cpu) / linux-job	3m 19s
unittests-linux (3.13, linux.g5.4xlarge.nvidia.gpu, cuda, 12.9) / linux-job	11m 54s
	15m 13s

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