Tests

Migrate extension-cpp to stable API/ABI #60

Job	Run time
unittests-linux (3.13, linux.g5.4xlarge.nvidia.gpu, cuda, 12.9) / linux-job	10m 7s
unittests-linux (3.11, linux.12xlarge, cpu) / linux-job	3m 14s
	13m 21s

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