Introduce Statistics Abstraction in Metadata in GIE

**Is your feature request related to a problem? Please describe.**

Currently, the CBO in GOpt relies on high-order statistics provided by GLogue for cost estimation, where GLogue further depends on low-order statistics information, namely the count of each vertex and edge type, to form its estimations. As of now, we simply retrieves (low-order) statistics information by reading from a file.

To enhance the modularity and scalability of our system, there's a need to refactor the way statistics are managed. This includes:

- [x] Introduce Statistics Abstraction in Metadata
- [x] In GOpt, build GLogue from Metadata

In Storages, Each storage should be responsible for providing its own statistics information, including:
- [x] ExpStore
- [x] Groot
- [ ] Vineyard
- [x] Mcsr
etc.