[Store] Change the operation of database, table and data parts from `meta` to `meta_node`

[ariesdevil]

Summary

The current implementation is to use meta directly, which needs to be changed to meta_node instead.

cc @dantengsky

[dantengsky]

Right! let's use meta_node instead, maybe we can drop "mem_engine"?

[ariesdevil]

Yup, if all operations are changed, mem_engine can be removed.

[dantengsky]

👍

if all operations are changed,

Pls follow your own plan, change the meta operations step by step is also fine, IMHO.

[ariesdevil]

👌🏻

[ariesdevil]

Closed by #1023