[SDK] Building block Network

[pepoviola]

Network high-level specs:

• We should allow to use a builder pattern to construct the network and the build method should create all the needed configuration to spawn the network.

• spawn method should check that all the needed artifacts are ready, and if not we should build internally.

• info method should return all the running config info (endpoints/chain-spec paths/ log paths/etc)

• destroy method should tear-down all the network and clean-up all the resources. (we want to allow to save the logs/database for a later analysis)

• rebuild should allow to rebuild the network instance from the same json we get from info.

[wirednkod]

Moved to paritytech/zombienet-sdk#2