feat: adding a new method to network config builder

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

@@ -271,6 +271,7 @@ pub async fn test_exex_context_with_chain_spec(
 
     let network_manager = NetworkManager::new(
         NetworkConfigBuilder::new(SecretKey::new(&mut rand::thread_rng()))
+            .with_unused_discovery_port()
             .build(provider_factory.clone()),
     )
     .await?;

crates/net/network/src/config.rs

@@ -347,6 +347,12 @@ impl NetworkConfigBuilder {
         self
     }
 
+    /// Sets the discovery port to an unused port.
+    /// This is useful for testing.
+    pub fn with_unused_discovery_port(self) -> Self {
+        self.discovery_port(0)
+    }
+
     /// Sets the external ip resolver to use for discovery v4.
     ///
     /// If no [`Discv4ConfigBuilder`] is set via [`Self::discovery`], this will create a new one.