CoralVM-C: Updated crl_core_bag struct

Removed the bag_length property, as the number of bag items can be read from string table. This also helped to reduce overall memory zone slot size from 32 to 28 bytes on 32bit Intel architectures and from 64 to 56 bytes on 64bit Intel architectures. However, the size of memory zone slot will likely increase in time, to store reference count and weak references linear linked list pointer.