Refactor batch prefetch #760

Job	Run time
sdist	9m 50s
macos-aarch64	9m 46s
macos-x86_64	9m 58s
linux (x86_64-unknown-linux-gnu)	7m 40s
linux-arm (aarch64-unknown-linux-gnu, aarch64, -e JEMALLOC_SYS_WITH_LG_PAGE=16)	10m 55s
linux (i686-unknown-linux-gnu)	11m 27s
windows (x86_64-pc-windows-msvc, x64)	14m 22s
linux-arm (armv7-unknown-linux-gnueabihf, armv7)	10m 31s
windows (i686-pc-windows-msvc, x86)	13m 47s
linux-powerpc (powerpc64le-unknown-linux-gnu, ppc64le, -e JEMALLOC_SYS_WITH_LG_PAGE=16)	10m 56s
linux-powerpc (powerpc64-unknown-linux-gnu, ppc64, -e JEMALLOC_SYS_WITH_LG_PAGE=16)	10m 47s
linux-arm (arm-unknown-linux-musleabihf, arm)	10m 15s
linux-s390x (s390x-unknown-linux-gnu, s390x)	14m 24s
musllinux (x86_64-unknown-linux-musl)	10m 22s
musllinux (i686-unknown-linux-musl)	8m 48s
musllinux-cross (aarch64-unknown-linux-musl, aarch64, -e JEMALLOC_SYS_WITH_LG_PAGE=16)	11m 16s
musllinux-cross (armv7-unknown-linux-musleabihf, armv7)	10m 39s
	3h 5m 43s

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