Remove RocksDB from subspace-node #508
Description
It is almost disablable in Substrate, by introducing a few additional feature flags it will be possible to disable it, which will speed-up node compilation significantly (also ParityDB uses less RAM, see paritytech/substrate#11513).
Disabling RocksDB means nodes will not be able to start after upgrade if they used RocksDB before (which is the case for CLI, desktop already uses ParityDB by default).