prev() function fails when non-element nodes are present (#30117)

The `prev()` function doesn't take nodes other than elements into account. Also we could simplify things a lot using the `previousElementSibling` property. This property isn't fully supported in IE, it only works for elements, but since the `element` variable is an element, we can safely use it here.

I've also added an additional test.

I don't think we had this issue in v4, since we relied on jQuery back then.

Ref. https://developer.mozilla.org/en-US/docs/Web/API/NonDocumentTypeChildNode/nextElementSibling

js/src/dom/selector-engine.js

@@ -56,19 +56,17 @@ const SelectorEngine = {
   },
 
   prev(element, selector) {
-    const siblings = []
+    let previous = element.previousElementSibling
 
-    let previous = element.previousSibling
-
-    while (previous && previous.nodeType === Node.ELEMENT_NODE && previous.nodeType !== NODE_TEXT) {
+    while (previous) {
       if (this.matches(previous, selector)) {
-        siblings.push(previous)
+        return [previous]
       }
 
-      previous = previous.previousSibling
+      previous = previous.previousElementSibling
     }
 
-    return siblings
+    return []
   }
 }