Improve exex test setup

[mattsse]

Describe the feature

ref

reth/crates/exex/test-utils/src/lib.rs

Lines 252 to 254 in c08c00f

	pub async fn test_exex_context_with_chain_spec(
	chain_spec: Arc<ChainSpec>,
	) -> eyre::Result<(ExExContext<Adapter>, TestExExHandle)> {

this has some limitations:

• the network always uses defaults

reth/crates/exex/test-utils/src/lib.rs

Lines 272 to 276 in c08c00f

	let network_manager = NetworkManager::new(
	NetworkConfigBuilder::new(SecretKey::new(&mut rand::thread_rng()))
	.build(provider_factory.clone()),
	)
	.await?;

but we use

reth/crates/exex/test-utils/src/lib.rs

Line 330 in c08c00f

config: NodeConfig::test(),

later the test setup uses random ports, so the network setup should also reflect that

see for ref

reth/crates/node/builder/src/builder/mod.rs

Lines 661 to 675 in c08c00f

	/// Get the [`NetworkConfigBuilder`].
	pub fn network_config_builder(&self) -> eyre::Result<NetworkConfigBuilder> {
	let secret_key = self.network_secret(&self.config().datadir())?;
	let default_peers_path = self.config().datadir().known_peers();
	let builder = self
	.config()
	.network
	.network_config(
	self.reth_config(),
	self.config().chain.clone(),
	secret_key,
	default_peers_path,
	)
	.with_task_executor(Box::new(self.executor.clone()))
	.set_head(self.head);

and

reth/crates/node/core/src/args/network.rs

Line 199 in c08c00f

pub fn network_config(

there's an opportunity to simply fn network_config and introduce one function that doesn't need the additional inputs

cc @loocapro paradigmxyz/reth-exex-examples#26

Additional context

No response