Decouple BackDrop from modal (#32439)

* Create backdrop.js util

* revert breaking changes

remove PromiseTimout usage

revert class name

* one more test | change bundlewatch.config

* add config obj to backdrop helper | tests for rootElement | use transitionend helper

* Minor tweaks — Renaming

Co-authored-by: Rohit Sharma <rohit2sharma95@gmail.com>

js/tests/unit/util/index.spec.js

@@ -568,4 +568,12 @@ describe('Util', () => {
       expect(typeof fakejQuery.fn.test.noConflict).toEqual('function')
     })
   })
+
+  describe('execute', () => {
+    it('should execute if arg is function', () => {
+      const spy = jasmine.createSpy('spy')
+      Util.execute(spy)
+      expect(spy).toHaveBeenCalled()
+    })
+  })
 })