Revert "Prefix scan: db_bench and bug fixes"

This reverts commit c2bd8f4824.

db/table_cache.h

@@ -52,12 +52,6 @@ class TableCache {
              void (*mark_key_may_exist)(void*) = nullptr,
              const bool no_io = false);
 
-  // Determine whether the table may contain the specified prefix.  If
-  // the table index of blooms are not in memory, this may cause an I/O
-  bool PrefixMayMatch(const ReadOptions& options, uint64_t file_number,
-                      uint64_t file_size, const Slice& internal_prefix,
-                      bool* table_io);
-
   // Evict any entry for the specified file number
   void Evict(uint64_t file_number);