Misleading RocksDb configuration

[elmattic]

Issue summary

The way we drive configuration of rocksdb with our RocksDbConfig could be better.

Right now it's a bit misleading:

Using a value for compaction_style of None will still result in rocksdb using compaction. We should always call ::set_disable_auto_compactions(bool) as the default value of this call is false.

Also verify if compression_type setting is ok.

Other information and links

https://docs.rs/rocksdb/latest/rocksdb/struct.Options.html#method.set_disable_auto_compactions