Improve `ndarray` integration #228

Job	Run time
rustfmt	2m 1s
conda (ubuntu, conda-forge, stable)	1m 16s
conda (windows, conda-forge, stable)	3m 46s
conda (macos, conda-forge, stable)	2m 2s
Address sanitizer	1m 35s
test apt (stable)	38s
static builds (ubuntu-latest, stable)	1m 19s
test apt (beta)	2m 10s
static builds (windows-latest, stable-msvc)	6m 32s
test apt (nightly)	2m 13s
static builds (windows-latest, stable-gnu)	5m 18s
static builds (macos-11, stable)	2m 58s
static builds (macos-latest, stable)	3m 33s
	35m 21s

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