fix(buffer): preserve stream consumer byte iteration

[andrewtdiz]

Summary

• Preserve exact byte iteration for Buffers returned by node:stream/consumers.buffer().
• Route Buffer Symbol.iterator lookups to values() while still respecting own symbol properties.
• Materialize small-slab Buffers as bytes in Array.from(buffer) before probing GC metadata.
• Add parity coverage and remove the now-passing buffer-byte-exact known failure.

Tests

• cargo fmt --all -- --check
• jq empty test-parity/known_failures.json
• git diff --check origin/main...HEAD
• ./scripts/check_file_size.sh
• ./run_parity_tests.sh --suite node-suite --module stream/consumers (33 pass, 0 fail)
• RUST_TEST_THREADS=1 cargo test -p perry-runtime (738 pass)
• CARGO_BUILD_JOBS=1 cargo test --workspace --exclude perry-runtime --exclude perry-ui-macos --exclude perry-ui-ios --exclude perry-ui-visionos --exclude perry-ui-tvos --exclude perry-ui-watchos --exclude perry-ui-gtk4 --exclude perry-ui-android --exclude perry-ui-windows

Non-goals

• Does not change stream pumping or the remaining stream pipeline/compose/web gaps.