[fuzz] Add Huffman round trip fuzzer

* Add a Huffman round trip fuzzer
* Fix two minor bugs in Huffman that aren't exposed in zstd
  - Incorrect weight comparison (weights are allowed to be equal to
    table log).
  - HUF_compress1X_usingCTable_internal() can return compressed
    size >= source size, so the assert that `cSize <= 65535` isn't
    correct, and it needs to be checked instead.

lib/common/entropy_common.c

@@ -299,7 +299,7 @@ HUF_readStats_body(BYTE* huffWeight, size_t hwSize, U32* rankStats,
     ZSTD_memset(rankStats, 0, (HUF_TABLELOG_MAX + 1) * sizeof(U32));
     weightTotal = 0;
     {   U32 n; for (n=0; n<oSize; n++) {
-            if (huffWeight[n] >= HUF_TABLELOG_MAX) return ERROR(corruption_detected);
+            if (huffWeight[n] > HUF_TABLELOG_MAX) return ERROR(corruption_detected);
             rankStats[huffWeight[n]]++;
             weightTotal += (1 << huffWeight[n]) >> 1;
     }   }