Completion: lower priority for override member items

#KT-9403 Fixed

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/CompletionUtils.kt

@@ -68,7 +68,7 @@ tailrec fun <T : Any> LookupElement.getUserDataDeep(key: Key<T>): T? {
 
 enum class ItemPriority {
     DEFAULT,
-    BACKING_FIELD,
+    OVERRIDE,
     NAMED_PARAMETER
 }
 

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/OverridesCompletion.kt

@@ -124,6 +124,8 @@ class OverridesCompletion(
                 }
             }
 
+            lookupElement.assignPriority(ItemPriority.OVERRIDE)
+
             collector.addElement(lookupElement)
         }
     }