Speed up emit_dist with precomputed length codings for static trees #1084

Job	Run time
cargo-c dynamic library	9s
QEMU build & test (stable, ubuntu-latest, s390x-unknown-linux-gnu, s390x-linux-gnu-gcc)	52s
Clippy	19s
QEMU build & test (stable, ubuntu-latest, i686-unknown-linux-gnu, i686-linux-gnu-gcc)	40s
Build and test (stable, ubuntu-latest, x86_64-unknown-linux-gnu)	1m 0s
Clippy (--no-default-features --features="c-allocator")	20s
Smoke-test fuzzing targets (default)	2m 36s
Clippy (--no-default-features --features="rust-allocator")	18s
Build and test (msrv, ubuntu-latest, x86_64-unknown-linux-gnu)	1m 3s
Smoke-test fuzzing targets (stable, macos-14, aarch64-apple-darwin)	2m 39s
Smoke-test fuzzing targets (c-allocator)	2m 30s
Build and test (beta, ubuntu-latest, x86_64-unknown-linux-gnu)	1m 4s
Smoke-test fuzzing targets (rust-allocator)	2m 32s
Build and test (stable, macos-latest, x86_64-apple-darwin)	1m 5s
vanilla dynamic library	13s
Build and test (stable, macos-14, aarch64-apple-darwin)	52s
Miri	1m 57s
Build and test (stable-x86_64-gnu, windows-2022, x86_64-pc-windows-gnu)	2m 36s
run flate2 test suite	17s
wasm32	35s
	23m 37s

Provide feedback