support bfloat16 in python #1704

Job	Run time
Linux x86_64 (cmake)	15m 23s
Linux x86_64 GPU w/ cuVS packages (CUDA 11.8.0)	0s
Linux arm64 packages	0s
Format	33s
Linux x86_64 GPU w/ cuVS packages (CUDA 12.4.0)	0s
Linux x86_64 GPU packages (CUDA 11.4.4)	0s
Linux x86_64 GPU packages (CUDA 12.1.1)	0s
Linux x86_64 packages	0s
OSX arm64 packages	0s
Windows x86_64 packages	0s
Linux x86_64 AVX2 (cmake)	15m 1s
Linux arm64 SVE (cmake)	14m 12s
Linux arm64 (conda)	11m 22s
Linux x86_64 AVX512 (cmake)	21m 28s
Linux x86_64 (conda)	26m 53s
Linux x86_64 GPU (cmake)	39m 19s
Linux x86_64 GPU w/ cuVS (cmake)	1h 44m 29s
Linux x86_64 GPU w/ ROCm (cmake)	30m 7s
Windows x86_64 (conda)	24m 7s
	5h 2m 54s

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