refactor: demote serialization failure from warning to debug

Serialization failures happen when recorded values misbehave but it is
not necessarily an unhappy path. There might good reasons why the
recorded programs have values that cannot be serialized. Also, this
message can be printed a lot so that alone would suffice for demotion.

components/serialization/default/index.mjs

@@ -17,7 +17,7 @@ const noargs = [];
 export default (dependencies) => {
   const {
     util: { assert, hasOwnProperty, coalesce, incrementCounter, createCounter },
-    log: { logWarning },
+    log: { logDebug },
   } = dependencies;
   const empty = symbolFor("APPMAP_EMPTY_MARKER");
   const wellknown = new _Set(
@@ -52,7 +52,7 @@ export default (dependencies) => {
         if (typeof name === "string") {
           return name;
         }
-        logWarning("failed to extract constructor name from %o", object);
+        logDebug("failed to extract constructor name from %o", object);
         return null;
       }
       object = getPrototypeOf(object);
@@ -121,7 +121,7 @@ export default (dependencies) => {
             try {
               serial.print = value.toString();
             } catch (error) {
-              logWarning("%o.toString() failure >> %O", value, error);
+              logDebug("%o.toString() failure >> %O", value, error);
               serial.print = apply(toString, value, noargs);
             }
           } else {