Use a single Vec between Decoder and ZlibStream #459

Job	Run time
powerpc_cross	15s
feature_check	1m 1s
build (1.57.0, ubuntu-latest)	2m 13s
rustfmt	4s
feature_check (benchmarks)	1m 0s
build (1.57.0, windows-latest)	3m 3s
test_all	55s
build (1.57.0, macos-latest)	3m 7s
build (stable, ubuntu-latest)	9s
build (stable, windows-latest)	33s
build (stable, macos-latest)	33s
build (beta, ubuntu-latest)	13s
build (beta, windows-latest)	51s
build (beta, macos-latest)	21s
build (nightly, ubuntu-latest)	17s
build (nightly, windows-latest)	45s
build (nightly, macos-latest)	26s
	15m 46s

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