Consider replace goleveldb

## Feature Request

### Describe your feature request related problem

PD uses goleveldb to store some of the less important metadata data, such as region information and historical hotspot information. As the number of data increases, the performance and resource consumption of goleveldb may not meet the demand. We may consider a more active community and low resource consumption with a high performance engine to replace it. such as [badger](https://github.com/dgraph-io/badger)

We need detailed testing and evaluation of the cost of compatibility processing.