Make module types explicit and convert some to ESM (#15964)

build-scripts/rollup-plugins/ignore-plugin.cjs

@@ -0,0 +1,24 @@
+module.exports = function (userOptions = {}) {
+  // Files need to be absolute paths.
+  // This only works if the file has no exports
+  // and only is imported for its side effects
+  const files = userOptions.files || [];
+
+  if (files.length === 0) {
+    return {
+      name: "ignore",
+    };
+  }
+
+  return {
+    name: "ignore",
+
+    load(id) {
+      return files.some((toIgnorePath) => id.startsWith(toIgnorePath))
+        ? {
+            code: "",
+          }
+        : null;
+    },
+  };
+};