Visualisation logging for sync batch states (#6034)

* Add visualization for batch states

* Replace icons with emojis

* Reviewers comments

* Change empty emoji and improve docs comments

* Fix lints

* Move to letters rather than emojis

* Replace 'V' with 'v'. Cargo update

* Merge latest unstable

* Improve docs around visualisation

* Merge branch 'unstable' into sync-batch-state

beacon_node/network/src/sync/range_sync/batch.rs

@@ -463,6 +463,11 @@ impl<E: EthSpec, B: BatchConfig> BatchInfo<E, B> {
             }
         }
     }
+
+    // Visualizes the state of this batch using state::visualize()
+    pub fn visualize(&self) -> char {
+        self.state.visualize()
+    }
 }
 
 /// Represents a peer's attempt and providing the result for this batch.
@@ -539,3 +544,19 @@ impl<E: EthSpec> std::fmt::Debug for BatchState<E> {
         }
     }
 }
+
+impl<E: EthSpec> BatchState<E> {
+    /// Creates a character representation/visualization for the batch state to display in logs for quicker and
+    /// easier recognition
+    fn visualize(&self) -> char {
+        match self {
+            BatchState::Downloading(..) => 'D',
+            BatchState::Processing(_) => 'P',
+            BatchState::AwaitingValidation(_) => 'v',
+            BatchState::AwaitingDownload => 'd',
+            BatchState::Failed => 'F',
+            BatchState::AwaitingProcessing(..) => 'p',
+            BatchState::Poisoned => 'X',
+        }
+    }
+}