fix(swingset): supervisor-xs: tolerate console.log(BigInt)

We serialize console.log arguments (to send over the pipe to the kernel
process) with JSON.stringify, which doesn't tolerate BigInt. Use a simple
replacer to turn them into Numbers first; we can tolerate the loss of
fidelity for console.log.

closes #2936

packages/SwingSet/src/kernel/vatManager/supervisor-subprocess-xsnap.js

@@ -108,6 +108,13 @@ function abbreviateReplacer(_, arg) {
   return arg;
 }
 
+function bigIntReplacer(_, arg) {
+  if (typeof arg === 'bigint') {
+    return Number(arg);
+  }
+  return arg;
+}
+
 /**
  * @param { ReturnType<typeof managerPort> } port
  */
@@ -123,7 +130,7 @@ function makeWorker(port) {
    */
   function makeConsole(tag) {
     const log = level => (...args) => {
-      const jsonSafeArgs = JSON.parse(`${q(args)}`);
+      const jsonSafeArgs = JSON.parse(JSON.stringify(args, bigIntReplacer));
       port.send(['console', level, tag, ...jsonSafeArgs]);
     };
     const cons = {