Move the public ZBUFF compatibility layer into the Rust static archive while
keeping stream contexts opaque and forwarding to the current ZSTD streaming
APIs. The deprecated C translation units are now declaration-only shims, so
the compatibility symbols work in compression-only and decompression-only
feature builds without duplicating private context layouts.
Test Plan:
- cargo test --manifest-path rust/Cargo.toml
- cargo clippy --manifest-path rust/Cargo.toml --all-targets -- -D warnings
- cargo +nightly fmt --manifest-path rust/Cargo.toml -- --check
- make -B -C lib libzstd.a ZSTD_LIB_DEPRECATED=1 V=1
- C ZBUFF compress/decompress smoke test against the rebuilt static archive
Depends-on: Rust compression and decompression streaming ABI ports