feat(compress): move CDict table copy leaf to Rust

ZSTD_copyCDictTableIntoCCtx only transformed tagged CDict match-table
entries or copied untagged entries; context-owned table selection remains in
C. Keep that policy and both call sites in C, forwarding the selected flag
through a narrow ABI. Rust removes the frozen eight-bit short-cache tag or
uses copy_nonoverlapping for C memcpy-equivalent copying without adding
validation.

Test Plan:
- Focused and full compression Rust tests passed (2 and 267 tests).
- `make -B -C lib -j2 lib` passed.
- `make -C tests -j2 fuzzer` passed.
- `./tests/fuzzer -s4560 -t47 -i48 -v` passed.
- Clippy normal/benches/tests before and after `cargo +nightly fmt` passed.
- `git diff --check` and `git diff --cached --check` passed.

lib/compress/zstd_compress.c

@@ -66,6 +66,8 @@ int ZSTD_rust_simpleCompress2Level(const void* cctx);
 int ZSTD_rust_simpleCompressStream2Level(const void* cctx);
 void ZSTD_rust_reduceTable(U32* table, U32 size, U32 reducerValue,
                            int preserveMark);
+void ZSTD_rust_copyCDictTableIntoCCtx(U32* dst, U32 const* src,
+                                      size_t tableSize, int tagged);
 U64 ZSTD_rust_advanceHashSalt(U64 hashSalt, U64 hashSaltEntropy);
 int ZSTD_rust_indexTooCloseToMax(size_t nextSrcBaseOffset);
 int ZSTD_rust_dictTooBig(size_t loadedDictSize);
@@ -1877,18 +1879,9 @@ ZSTD_resetCCtx_byAttachingCDict(ZSTD_CCtx* cctx,
 
 static void ZSTD_copyCDictTableIntoCCtx(U32* dst, U32 const* src, size_t tableSize,
                                         ZSTD_compressionParameters const* cParams) {
-    if (ZSTD_CDictIndicesAreTagged(cParams)){
-        /* Remove tags from the CDict table if they are present.
-         * See docs on "short cache" in zstd_compress_internal.h for context. */
-        size_t i;
-        for (i = 0; i < tableSize; i++) {
-            U32 const taggedIndex = src[i];
-            U32 const index = taggedIndex >> ZSTD_SHORT_CACHE_TAG_BITS;
-            dst[i] = index;
-        }
-    } else {
-        ZSTD_memcpy(dst, src, tableSize * sizeof(U32));
-    }
+    ZSTD_STATIC_ASSERT(ZSTD_SHORT_CACHE_TAG_BITS == 8);
+    ZSTD_rust_copyCDictTableIntoCCtx(dst, src, tableSize,
+                                     ZSTD_CDictIndicesAreTagged(cParams));
 }
 
 static size_t ZSTD_resetCCtx_byCopyingCDict(ZSTD_CCtx* cctx,