LevelDB vs RocksDB

[wrkzdev]

We have made some test benchmark between RocksDB (existing) and LevelDB for upcoming upgrade as an alternative.

* WrkzCoin daemon importing speed comparison from bootstrap
https://www.youtube.com/watch?v=rZ0Kf1DkcKM

* Wallet sync speed comparison for WrkzCoin between RocksDB vs LevelDB
https://www.youtube.com/watch?v=l20Bt62JD9k

* (ARM64-2GB) Wallet sync speed comparison for WrkzCoin between RocksDB vs LevelDB
https://www.youtube.com/watch?v=uHFen3-E5rE

Based on the tests, LevelDB is well performed. LevelDB is already existed in development branch of WrkzCoin repo: https://github.com/wrkzcoin/wrkzcoin