cmp: stop allocating for byte printing #540

Job	Run time
cargo fmt --all -- --check	8s
GNU test suite	50s
cargo clippy -- -D warnings (macOS-latest)	18s
cargo check (windows-latest)	39s
cargo check (macOS-latest)	13s
cargo clippy -- -D warnings (windows-latest)	1m 12s
Code Coverage (ubuntu-latest, unix)	1m 54s
Code Coverage (macos-latest, macos)	3m 10s
cargo clippy -- -D warnings (ubuntu-latest)	16s
cargo test (macOS-latest)	2m 24s
Code Coverage (windows-latest, windows)	6m 57s
cargo check (ubuntu-latest)	17s
cargo test (ubuntu-latest)	39s
cargo test (windows-latest)	4m 31s
	23m 28s

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