feat(compress): move streaming size helpers to Rust

The public streaming-size functions still calculated their values in the C
compressor entry point. Keep those public symbols and their size_t ABI in C,
but route the pure formulas through zstd_compress_api.rs. Rust uses usize for
the C size_t-equivalent constants and reuses its compressBound implementation;
the fixed block and header sizes make the output helper exactly 131591 bytes.

Test Plan:
- Focused Rust cstream size test -- passed (1 test)
- make -B -C lib -j2 lib -- passed
- make -C tests -j2 fuzzer -- passed
- ./tests/fuzzer -s4560 -t47 -i48 -v -- passed
- Required clippy, nightly fmt, and staged diff checks -- passed

lib/compress/zstd_compress.c

@@ -79,6 +79,8 @@ int ZSTD_rust_targetCBlockSizeAction(int bss, int isFirstBlock,
                                      int maybeRLE, int isRLE,
                                      size_t cSize, size_t srcSize,
                                      int strategy);
+size_t ZSTD_rust_CStreamInSize(void);
+size_t ZSTD_rust_CStreamOutSize(void);
 
 /* Context-free compression-parameter selection and sizing leaves live in
  * Rust (rust/src/zstd_compress_params.rs).  This file retains
@@ -4384,11 +4386,11 @@ size_t ZSTD_freeCStream(ZSTD_CStream* zcs)
 
 /*======   Initialization   ======*/
 
-size_t ZSTD_CStreamInSize(void)  { return ZSTD_BLOCKSIZE_MAX; }
+size_t ZSTD_CStreamInSize(void)  { return ZSTD_rust_CStreamInSize(); }
 
 size_t ZSTD_CStreamOutSize(void)
 {
-    return ZSTD_compressBound(ZSTD_BLOCKSIZE_MAX) + ZSTD_blockHeaderSize + 4 /* 32-bits hash */ ;
+    return ZSTD_rust_CStreamOutSize();
 }
 
 static ZSTD_CParamMode_e ZSTD_getCParamMode(ZSTD_CDict const* cdict, ZSTD_CCtx_params const* params, U64 pledgedSrcSize)