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

gulpfile.js

@@ -1,3 +1,13 @@
-var requireDir = require("require-dir");
+import { globIterate } from "glob";
 
-requireDir("./build-scripts/gulp/");
+const gulpImports = [];
+
+for await (const gulpModule of globIterate("build-scripts/gulp/*.?(c|m)js", {
+  dotRelative: true,
+})) {
+  gulpImports.push(import(gulpModule));
+}
+
+// Since all tasks are currently registered with gulp.task(), this is enough
+// If any are converted to named exports, need to loop and aggregate exports here
+await Promise.all(gulpImports);