feat(amx): public ndarray-typed matmul API (#119, sprint A4) #220

Job	Run time
Pass MSRV values to other jobs	3s
format/stable	29s
clippy/stable	47s
miri	30s
cross_test/s390x-unknown-linux-gnu/stable	1m 44s
cargo-careful	34s
nostd/thumbv6m-none-eabi/stable	38s
native-backend/stable	1m 20s
cross_test/i686-unknown-linux-gnu/stable	1m 47s
docs/nightly	59s
blas-msrv	1m 0s
tests/beta	1m 7s
tests/1.64.0	56s
tests/stable	1m 15s
conclusion	0s
	13m 9s

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