Translate the frozen v0.2 frame, entropy, block, frame-size, and streaming
decoder paths to Rust while preserving the opaque C context ABI. Replace the
3465-line historical C implementation with a declaration-only shim and enable
the Rust module for the legacy-v02 Cargo feature.
Test Plan:
- cargo test --manifest-path rust/Cargo.toml --no-default-features --features compression,decompression,dict-builder,legacy-v02
- make -B -C lib libzstd.a ZSTD_LEGACY_SUPPORT=2 V=1
- git diff --check
Refs: rust/src/legacy/zstd_v02.rs, lib/legacy/zstd_v02.c
ddidderr
9b909aaef8