Make RelayPool private to NostrNetworkManager and migrate usages

Signed-off-by: Daniel D’Aquino <daniel@daquino.me>

highlighter action extension/ActionViewController.swift

@@ -164,7 +164,7 @@ struct ShareExtensionView: View {
                 break
             case .active:
                 print("txn: 📙 HIGHLIGHTER ACTIVE")
-                state.nostrNetwork.pool.ping()
+                state.nostrNetwork.ping()
             @unknown default:
                 break
             }