implement dot for higher-dimensional arrays with Ix2 #669

Job	Run time
docs/nightly	19s
Pass MSRV values to other jobs	3s
miri	10m 52s
format/nightly	15s
cross_test/i686-unknown-linux-gnu/stable	2m 12s
clippy/stable	19s
nostd/thumbv6m-none-eabi/stable	19s
cargo-careful	1m 50s
cross_test/s390x-unknown-linux-gnu/stable	8m 41s
blas-msrv	37s
tests/nightly	2m 46s
tests/1.87.0	2m 30s
tests/beta	2m 24s
tests/stable	2m 32s
conclusion	2s
	35m 41s

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