DEV: Update ember-qunit to 6.0.0 (#19080)

Long story short - bumping ember-qunit upgrades webpack, and sinon is not compatible with webpack v5. It uses node's `util` module and that is no longer polyfilled by webpack by default.

This PR adds the `util` polyfill (😑, but what can you do) and also injects a stub of `process` (so polyfill + sinon actually work)

app/assets/javascripts/discourse/ember-cli-build.js

@@ -64,6 +64,26 @@ module.exports = function (defaults) {
         optimization: {
           moduleIds: "size", // Consistent module references https://github.com/ef4/ember-auto-import/issues/478#issuecomment-1000526638
         },
+        resolve: {
+          fallback: {
+            util: require.resolve("util/"),
+          },
+        },
+        module: {
+          rules: [
+            {
+              test: require.resolve("util/"),
+              use: [
+                {
+                  loader: "imports-loader",
+                  options: {
+                    additionalCode: "var process = { env: {} };",
+                  },
+                },
+              ],
+            },
+          ],
+        },
       },
     },
     fingerprint: {

app/assets/javascripts/discourse/package.json

@@ -68,7 +68,7 @@
     "ember-load-initializers": "^2.1.1",
     "ember-modifier": "^3.2.7",
     "ember-on-resize-modifier": "^1.1.0",
-    "ember-qunit": "^5.1.5",
+    "ember-qunit": "^6.0.0",
     "ember-rfc176-data": "^0.3.17",
     "ember-source": "~3.28.10",
     "ember-test-selectors": "^6.0.0",
@@ -108,6 +108,8 @@
   "devDependencies": {
     "ember-cached-decorator-polyfill": "^1.0.1",
     "ember-cli-deprecation-workflow": "^2.1.0",
-    "ember-exam": "^8.0.0"
+    "ember-exam": "^8.0.0",
+    "imports-loader": "^4.0.1",
+    "util": "^0.12.5"
   }
 }