Revamp the `Pixel` trait via the `pixeli` crate #1439

Job	Run time
test_other_archs (powerpc-unknown-linux-gnu)	2m 37s
test_avif_decoding	1m 27s
test_features	30s
test_other_archs (i686-unknown-linux-gnu)	1m 34s
test_toolchains (1.67.1)	33s
test_features (default)	1m 44s
test_toolchains (nightly)	1m 6s
test_features (rayon)	30s
test_toolchains (beta)	1m 25s
build_benchmarks	46s
test_features (avif)	1m 1s
Fuzz targets (afl)	2m 28s
test_features (bmp)	20s
Fuzz targets (cargo-fuzz)	53s
cargo-deny	20s
cargo-semver-checks	30s
test_features (dds)	19s
clippy	2m 3s
test_features (exr)	34s
public_private_dependencies	28s
rustfmt	10s
test_features (ff)	36s
test_features (gif)	25s
test_features (hdr)	21s
test_features (ico)	25s
test_features (jpeg)	21s
test_features (png)	27s
test_features (pnm)	33s
test_features (qoi)	17s
test_features (tga)	25s
test_features (tiff)	30s
test_features (webp)	38s
	26m 16s

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