Rework index manipulation API #1658

Job	Run time
setup-matrix	6s
Tests (cuda, ubuntu-latest, Julia 1)	1m 28s
Tests (factorizations, ubuntu-latest, Julia 1)	12m 7s
Tests (amd, ubuntu-latest, Julia 1)	1m 22s
Tests (symmetries, ubuntu-latest, Julia 1)	11m 23s
Tests (chainrules, ubuntu-latest, Julia 1)	29m 12s
Tests (other, ubuntu-latest, Julia 1)	2m 57s
Tests (tensors, ubuntu-latest, Julia 1)	17m 49s
Tests (mooncake, ubuntu-latest, Julia 1)	29m 19s
	1h 45m 43s

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