[fuzz] Dividing by targetCBlockSize instead of blockSize for nbBlocks fit (#1936)

* Adding fail logging for superblock flow

* Dividing by targetCBlockSize instead of blockSize

* Adding new const and using more acurate formula for nbBlocks

* Only do dstCapacity check if using superblock

* Remvoing disabling logic

* Updating test to make it catch more extreme case of previou bug

* Also updating comment

* Only taking compressEnd shortcut on non-superblock

lib/common/zstd_internal.h

@@ -128,6 +128,8 @@ static const size_t ZSTD_did_fieldSize[4] = { 0, 1, 2, 4 };
 static const size_t ZSTD_blockHeaderSize = ZSTD_BLOCKHEADERSIZE;
 typedef enum { bt_raw, bt_rle, bt_compressed, bt_reserved } blockType_e;
 
+#define ZSTD_FRAMECHECKSUMSIZE 4
+
 #define MIN_SEQUENCES_SIZE 1 /* nbSeq==0 */
 #define MIN_CBLOCK_SIZE (1 /*litCSize*/ + 1 /* RLE or RAW */ + MIN_SEQUENCES_SIZE /* nbSeq==0 */)   /* for a non-null block */