Miles

I added PebbleDB unit test into `db_manager_test.go`. and the tests I changed run successfully on my local machine. However, Im not sure why the CI jobs failed. (with below log)...

I added metrics and all the logic from [pebble.go](https://github.com/ethereum/go-ethereum/blob/master/ethdb/pebble/pebble.go#L455) in Geth Do I need to make the metrics key the same as in the [leveldb_database.go](https://github.com/klaytn/klaytn/blob/dev/storage/database/leveldb_database.go#L358) code? ```diff - d.compWriteMeter =...

NOTE: I need to refer to the [RocksDB PR](https://github.com/klaytn/klaytn/pull/1855)

Ok, I will bring all the comments.

@blukat29 Ok, I will move PR to Kaia by the end of this week. thank you.

Ok Here is the new PR: https://github.com/kaiachain/kaia/pull/42