Revive network-test logs files in CI (#7459)

https://github.com/sigp/lighthouse/issues/7187


  This PR adds a writer that implements `tracing_subscriber::fmt::MakeWriter`, which writes logs to separate files for each test.

beacon_node/network/src/sync/tests/lookups.rs

@@ -107,6 +107,8 @@ impl TestRig {
         // deterministic seed
         let rng = ChaCha20Rng::from_seed([0u8; 32]);
 
+        init_tracing();
+
         TestRig {
             beacon_processor_rx,
             beacon_processor_rx_queue: vec![],