ZK Stack node initialization framework.

This crate provides core abstractions that allow one to compose a ZK Stack node. Main concepts used in this crate are:

• WiringLayer - builder interface for tasks.
• Task - a unit of work that can be executed by the node.
• Resource - a piece of logic that can be shared between tasks. Most resources are represented by generic interfaces and also serve as points of customization for tasks.
• ZkStackService - a container for tasks and resources that takes care of initialization, running and shutting down.
• ZkStackServiceBuilder - a builder for the service.