Use core::mem::transmute instead of std in wasm adler32

[storo-dfend]

When compiling zlib_rs for wasm32-unknown-unknown with default-features = false, the build fails because zlib-rs/src/adler32/wasm.rs uses std::mem::transmute. This PR uses core::mem::transmute instead, since it does the same job and doesn't break no_std builds.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Flag	Coverage Δ
fuzz-compress	?
fuzz-decompress	?
test-aarch64-apple-darwin	93.25% <ø> (-0.02%)	⬇️
test-x86_64-apple-darwin	91.70% <ø> (-0.03%)	⬇️
test-x86_64-unknown-linux-gnu	90.24% <ø> (-0.01%)	⬇️

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see 6 files with indirect coverage changes

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[folkertdev]

Thanks!