Move back the 'KotlinStructureViewElement.isPublic' property used externally

Reasoning: Method com.gmail.blueboxware.extsee.kotlin.ExtSeeKotlinStructureViewModel.Companion.PublicElementsFilter.isVisible(com.intellij.ide.util.treeView.smartTree.TreeElement treeNode) : boolean contains an *invokevirtual* instruction referencing an unresolved method org.jetbrains.kotlin.idea.structureView.KotlinStructureViewElement.isPublic()

idea/idea-analysis/src/org/jetbrains/kotlin/idea/structureView/KotlinStructureViewElement.kt

@@ -44,6 +44,13 @@ class KotlinStructureViewElement(
                 KotlinStructureElementPresentation(isInherited, element, countDescriptor())
             }
 
+    @Deprecated("Use 'visibility' instead.", level = DeprecationLevel.ERROR)
+    var isPublic
+            by AssignableLazyProperty {
+                isPublic(countDescriptor())
+            }
+        private set
+
     var visibility
             by AssignableLazyProperty {
                 Visibility(countDescriptor())
@@ -103,6 +110,9 @@ class KotlinStructureViewElement(
         return result
     }
 
+    private fun isPublic(descriptor: DeclarationDescriptor?) =
+        (descriptor as? DeclarationDescriptorWithVisibility)?.visibility == Visibilities.PUBLIC
+
     private fun countDescriptor(): DeclarationDescriptor? {
         val element = element
         return when {