feat(quantized): GGUF-compat Q4_0 quant/dequant (#120, sprint A5) #221

Job	Run time
miri	31s
docs/nightly	50s
native-backend/stable	1m 18s
cross_test/i686-unknown-linux-gnu/stable	1m 47s
clippy/stable	47s
Pass MSRV values to other jobs	3s
cargo-careful	42s
nostd/thumbv6m-none-eabi/stable	36s
cross_test/s390x-unknown-linux-gnu/stable	1m 41s
format/stable	33s
blas-msrv	55s
tests/1.64.0	1m 7s
tests/stable	1m 10s
tests/beta	59s
conclusion	-1s
	12m 58s

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