perf: remove dtype + fill val handling per chunk #363

Job	Run time
build sdist	17s
build on linux (x86_64 - 2_28)	4m 47s
build on macos (x86_64)	4m 40s
build on linux (aarch64 - musllinux_1_2)	4m 8s
build on windows (x86_64)	12m 3s
build on macos (aarch64)	3m 21s
build on linux (aarch64 - 2_28)	4m 15s
build on linux (armv7 - 2_28)	4m 1s
build on linux (armv7 - musllinux_1_2)	4m 8s
build on linux (ppc64le - 2_28)	4m 17s
build on linux (x86_64 - musllinux_1_2)	4m 17s
inspect	4s
version	0s
publish	0s
	50m 18s

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