imp: until legacy is removed, accommodate min legacy trace cfg in new trace cfg

Author: johnalotoski

cardano-lib/generic-log-config.nix

@@ -207,4 +207,11 @@
   # Required by the legacy tracing system, this key is still required for
   # cardano-node to start.
   minSeverity = "Critical";
+
+  # Required by some legacy tests which may otherwise fail to start.
+  defaultBackends = [];
+  defaultScribes = [];
+  options = {};
+  setupBackends = [];
+  setupScribes = [];
 }

cardano-lib/testnet-template/config.json

@@ -120,5 +120,10 @@
   "TurnOnLogMetrics": true,
   "TurnOnLogging": true,
   "UseTraceDispatcher": true,
-  "minSeverity": "Critical"
+  "defaultBackends": [],
+  "defaultScribes": [],
+  "minSeverity": "Critical",
+  "options": {},
+  "setupBackends": [],
+  "setupScribes": []
 }