implement dot for higher-dimensional arrays with Ix2 #677

Job	Run time
Pass MSRV values to other jobs	3s
cross_test/i686-unknown-linux-gnu/stable	2m 44s
format/nightly	15s
docs/nightly	20s
cross_test/s390x-unknown-linux-gnu/stable	7m 50s
clippy/stable	28s
nostd/thumbv6m-none-eabi/stable	21s
miri	8m 13s
cargo-careful	2m 6s
blas-msrv	1m 1s
tests/nightly	3m 33s
tests/beta	3m 10s
tests/stable	3m 8s
tests/1.87.0	3m 7s
conclusion	2s
	36m 21s

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