[Feature]: cheap store renaming migration

[yihuang]

Summary

Currently to rename a store in upgrade, it renames all the existing keys in that store, which is very heavy.
We propose a cheap way to do that.

Problem Definition

No response

Proposed Feature

We had cheap renaming in memiavl, I think the idea can be adapted to iavl as well similarly. The idea is to maintain a version-ed logical name to physical name mapping, to rename a store, we simply change the logical name in the mapping.

{prefix}-{version}: [(logical store name, physical store name)]

When load a multistore, we load the store name mapping into memory as well, and handle the name conversion accordingly.

The mapping should be stored in a version-ed way, and only save to db when modified, when loading a multistore, we should seek the correct version of the mapping based on target version.

The map is small, renaming operations are not frequent, performance overhead should be very small.