Redundant genesis state is created even if a node is started from a snapshot

When a `VirtualMapStateLifecycleManager` instance is created, it constructs a new empty `VirtualMap` right in the constructor. This is done even if the lifecycle manager will later be used to load a state from a snapshot using `loadSnapshot()` method. The genesis state will be just thrown away in this case.

Creating a virtual map is not free. It initializes a node cache and builds a MerkleDb data source, which includes working with multiple different files. This affects node startup time. It would be better to avoid creating this extra genesis state at startup if it isn't needed.