Refactor Test Utils

[samliok]

This PR refactors the testutil package to better decouple testing helpers and make it easier to compose custom networks, nodes, block builders, and related components.

The refactor introduces a set of building blocks, such as BasicNode and BasicNetwork that encapsulate shared responsibilities like epoch message handling, lifecycle management (start/stop), and essential helper functionality. These primitives can then be composed to build more specialized testing environments, such as LongRunningNetwork or ControlledInMemoryNetwork.

Specialized networks and nodes are responsible for their own additional behavior (e.g., custom block builders, node crash logic, or test-specific helpers), rather than inheriting unused functionality. This avoids the need for a single, monolithic network or node type that accumulates features required only by a subset of tests, keeping the test infrastructure more modular and extensible.

[yacovm]

This is just like the new code:

func (b *BasicNode) RecordMessageTypeSent(msg *simplex.Message) {
	switch {
	case msg.BlockMessage != nil:
		b.messageTypesSent["BlockMessage"]++
	case msg.VerifiedBlockMessage != nil:
		b.messageTypesSent["VerifiedBlockMessage"]++
	case msg.ReplicationRequest != nil:
		b.messageTypesSent["ReplicationRequest"]++
	case msg.ReplicationResponse != nil:
		b.messageTypesSent["ReplicationResponse"]++
	case msg.Notarization != nil:
		b.messageTypesSent["VerifiedReplicationRequest"]++
	case msg.VerifiedReplicationResponse != nil:
		b.messageTypesSent["VerifiedReplicationResponse"]++
	case msg.Finalization != nil:
		b.messageTypesSent["NotarizationMessage"]++
	case msg.FinalizeVote != nil:
		b.messageTypesSent["FinalizationMessage"]++
	case msg.VoteMessage != nil:
		b.messageTypesSent["VoteMessage"]++
	case msg.EmptyVoteMessage != nil:
		b.messageTypesSent["EmptyVoteMessage"]++
	case msg.EmptyNotarization != nil:
		b.messageTypesSent["EmptyNotarization"]++
	case msg.BlockDigestRequest != nil:
		b.messageTypesSent["BlockDigestRequest"]++
	default:
		panic("unknown message type")
	}
}

Was this file moved and then changed? or was the code just copied?

Is there a way to reduce the diff by git mv and then applying the code changes?

[yacovm]

license header

[samliok]

added all

[yacovm]

can be merged after adding license header