feat(quantized): GGUF-compat Q4_0 quant/dequant for burn QuantValue::Q4F/Q4S (sprint A5) #205

Job	Run time
format/stable	29s
clippy/stable	43s
nostd/thumbv6m-none-eabi/stable	38s
cross_test/s390x-unknown-linux-gnu/stable	1m 49s
cross_test/i686-unknown-linux-gnu/stable	1m 52s
native-backend/stable	51s
Pass MSRV values to other jobs	4s
miri	0s
docs/nightly	0s
cargo-careful	0s
blas-msrv	57s
tests/stable	1m 2s
tests/beta	1m 6s
tests/1.64.0	56s
conclusion	-1s
	10m 26s

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