implement dot for higher-dimensional arrays with Ix2 #680

Job	Run time
nostd/thumbv6m-none-eabi/stable	20s
miri	11m 9s
Pass MSRV values to other jobs	3s
format/nightly	14s
clippy/stable	23s
docs/nightly	21s
cargo-careful	1m 47s
cross_test/s390x-unknown-linux-gnu/stable	8m 25s
cross_test/i686-unknown-linux-gnu/stable	2m 11s
blas-msrv	47s
tests/nightly	2m 54s
tests/beta	2m 24s
tests/1.87.0	2m 36s
tests/stable	2m 25s
conclusion	3s
	36m 2s

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