Preload doesn't load in sandboxed render if preload path contains special chars (#12037)

* Adding missing headers

* adding ut

* Removing the file path exists check

* fixing test

* exposing window.require in UT

spec/fixtures/module/preload-sandboxæø åü.js

@@ -0,0 +1,6 @@
+(function () {
+  window.require = require
+  if (location.protocol === 'file:') {
+    window.test = 'preload'
+  }
+})()