MDEV-12930 Testing SEQUENCE object

Fixed the following things from the above MDEV:
- Ensure the user has INSERT privilege when generating new sequence values
  with NEXT VALUE FOR or SETVAL()
- Fixed bug in InnoDB when generating several sequence values in one statement
- Ensure that read_set is up to date before calling ha_sequence::ha_write_row()
  - This is only a potential bug with storage engines that trusts the column maps completely

sql/ha_sequence.h

@@ -152,6 +152,8 @@ public:
   { return file->check_and_repair(thd); }
   bool is_crashed() const
   { return file->is_crashed(); }
+  void column_bitmaps_signal()
+  { return file->column_bitmaps_signal(); }
 
   /* New methods */
   void register_original_handler(handler *file_arg)