Simplify cargo features exposed by the crate #910

Job	Run time
test_toolchains (1.64.0)	1m 38s
test_toolchains (nightly)	24s
test_toolchains (beta)	25s
test_avif	1m 42s
test_big_endian	42s
test_big_endian (default)	42s
test_big_endian (webp)	40s
test_big_endian (webp-encoder)	19s
test_features	1m 17s
test_features (default)	3m 57s
test_features (gif)	1m 6s
test_features (jpeg)	1m 21s
test_features (png)	1m 14s
test_features (tiff)	1m 30s
test_features (ico)	1m 26s
test_features (pnm)	1m 21s
test_features (tga)	59s
test_features (webp)	59s
test_features (bmp)	1m 19s
test_features (hdr)	1m 23s
test_features (dxt)	1m 22s
test_features (dds)	1m 10s
test_features (farbfeld)	26s
test_features (openexr)	18s
test_features (jpeg_rayon)	19s
test_features (webp-encoder)	26s
build_benchmarks	1m 37s
Fuzz targets (afl)	2m 12s
Fuzz targets (cargo-fuzz)	4m 59s
cargo-deny	26s
clippy	4m 29s
public_private_dependencies	44s
rustfmt	15s
test_avif_decoding	1m 5s
verify_msrv	2m 17s
	46m 29s

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