Update MSRV and fix clippy issues #1200

Job	Run time
build_benchmarks	41s
Fuzz targets (cargo-fuzz)	5m 37s
cargo-deny	22s
Fuzz targets (afl)	1m 30s
clippy	2m 7s
public_private_dependencies	17s
rustfmt	22s
test_avif_decoding	2m 18s
test_avif	1m 10s
test_features	24s
test_other_archs (powerpc-unknown-linux-gnu, default)	4m 14s
test_features (default)	1m 44s
verify_msrv	3m 23s
test_other_archs (powerpc-unknown-linux-gnu, webp-encoder)	2m 46s
test_toolchains (1.61.0)	1m 1s
test_features (gif)	50s
test_other_archs (i686-unknown-linux-gnu, default)	2m 12s
test_toolchains (nightly)	2m 12s
test_features (jpeg)	30s
test_other_archs (i686-unknown-linux-gnu, webp-encoder)	1m 41s
test_toolchains (beta)	1m 50s
test_features (png)	35s
test_features (tiff)	33s
test_features (ico)	43s
test_features (pnm)	31s
test_features (tga)	27s
test_features (webp)	31s
test_features (bmp)	33s
test_features (hdr)	33s
test_features (dxt)	1m 2s
test_features (dds)	29s
test_features (farbfeld)	28s
test_features (openexr)	41s
test_features (jpeg_rayon)	33s
test_features (webp-encoder)	49s
	45m 39s

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