Don't mix ESM and CommonJS in shim/dynamic.js

It seems that at some point when this was written someone mixed ESM and
CommonJS syntax.

There is not good reason to do this, and it will soon not be supported -
and arguably has never been, it just happened to work due to how ESM was
supported in k6.

See grafana/k6#3807 and linked issues/PRs

lib/shim/dynamic.js

@@ -198,7 +198,7 @@ const DIRECTORY_PATHS = [
 ];
 
 // generators for $random* variables
-const dynamicGenerators = {
+export const dynamicGenerators = {
   // Skipped from Postman
   $guid: {
     description: 'A v4 style guid',
@@ -756,7 +756,7 @@ const dynamicGenerators = {
 // It will look like this: /\{\{\$guid\}\}|\{\{\$timestamp\}\}|\{\{\$isoTimestamp\}\}/g
 // It can then be used to match templates containing generators
 // for example with the replaceIn function
-const dynamicGeneratorsRegex = (function() {
+export const dynamicGeneratorsRegex = (function() {
   let generatorRegexString = '';
   for (const [key, value] of Object.entries(dynamicGenerators)) {
     generatorRegexString += '{{' + key + '}}' + '|';
@@ -770,8 +770,3 @@ const dynamicGeneratorsRegex = (function() {
   const generatorRegex = new RegExp(generatorRegexString, 'g');
   return generatorRegex;
 })();
-
-module.exports = {
-  dynamicGenerators,
-  dynamicGeneratorsRegex,
-};