Event-based block lookup tests (#5534)

* WIP

* Initial working version of new sync tests.

* Remove sync traits and fix lints.

* Reduce internal method visibility and make test method instead. Remove extra beacon chain harness instance created in tests.

* Improve `SyncTester` api.

* Fix lint.

* Test example

* Lookup tests using rig

* Tests should interface with events only

* lint

* Skip deneb test pre-deneb

* Add more assertions

* Remove logging changes

* Address @jimmygchen comments

* Merge branch 'unstable' of https://github.com/sigp/lighthouse into bn-p2p-tests

* remove unused assertions

* fix lint

beacon_node/network/src/sync/block_lookups/mod.rs

@@ -76,6 +76,24 @@ impl<T: BeaconChainTypes> BlockLookups<T> {
         }
     }
 
+    #[cfg(test)]
+    pub(crate) fn active_single_lookups(&self) -> Vec<Id> {
+        self.single_block_lookups.keys().cloned().collect()
+    }
+
+    #[cfg(test)]
+    pub(crate) fn active_parent_lookups(&self) -> Vec<Hash256> {
+        self.parent_lookups
+            .iter()
+            .map(|r| r.chain_hash())
+            .collect::<Vec<_>>()
+    }
+
+    #[cfg(test)]
+    pub(crate) fn failed_chains_contains(&mut self, chain_hash: &Hash256) -> bool {
+        self.failed_chains.contains(chain_hash)
+    }
+
     /* Lookup requests */
 
     /// Creates a lookup for the block with the given `block_root` and immediately triggers it.