Refactor online nodes.

[facuMH]

This PR adds health checks to verify that nodes are actively producing blocks after being added to the network, ensuring the network is in a healthy state before proceeding.

Changes

• New: OperaNode.CheckBlockProducing(ctx):
  • Streams the container logs and waits until at least 2 "New block" lines with strictly increasing block indices are observed.
  • Respects context cancellation/deadline for timeout control.
  • Returns an error if the log stream ends prematurely or the timeout expires before the condition is met.
• New: LocalNetwork.WaitForBlockProduction(ctx):
  • Runs CheckBlockProducing on all nodes in the network in parallel.
  • Returns joined errors for any nodes that failed to produce blocks within the deadline.

Modified

• LocalNetwork.createNode:
  • After addNodeIntoNetwork (peering), the flow now:
    • Calls CheckBlockProducing on the newly added node (30s timeout)
    • Calls WaitForBlockProduction to confirm all nodes in the network are producing blocks
    • Only then fires AfterNodeCreation listeners

This should help ensures that by the time a node is considered "ready", both the new node and the existing network are actively producing blocks — not just that docker container is running.