Array.copyOf docs: do not use 'primitive default' term, rewrite description

#KT-22298

libraries/tools/kotlin-stdlib-gen/src/templates/Arrays.kt

@@ -446,11 +446,11 @@ object ArrayOps : TemplateGroupBase() {
     } builder {
         doc {
             """
-            Returns new array which is a copy of the original array, resized to the given [newSize],
-            truncating original values or padding new array with ${if(family == ArraysOfPrimitives) "primitive default" else "null"} values if necessary.
+            Returns new array which is a copy of the original array, resized to the given [newSize].
+            The copy is either truncated or padded at the end with ${primitive.zero} values if necessary.
 
-            For all indices that are valid in both the original array and the copy, the two arrays contents will be identical.
-            For all indices that are valid in the copy, but not in the original, the copy will contain ${if(family == ArraysOfPrimitives) "primitive default" else "null"} values.
+            - If [newSize] is less than the size of the original array, the copy array is truncated to the [newSize].
+            - If [newSize] is greater than the size of the original array, the extra elements in the copy array are filled with ${primitive.zero} values.
             """
         }
         specialFor(ArraysOfPrimitives) {

libraries/tools/kotlin-stdlib-gen/src/templates/dsl/FamilyProperties.kt

@@ -43,6 +43,14 @@ object DocExtensions {
             else -> "list"
         }
 
+    val PrimitiveType?.zero: String
+        get() = when (this) {
+            null -> "`null`"
+            PrimitiveType.Boolean -> "`false`"
+            PrimitiveType.Char -> "null char (`\\u0000`)"
+            else -> "zero"
+        }
+
     fun textWhen(condition: Boolean, text: () -> String): String = if (condition) text() else ""
 
     private fun String.singularize() = removeSuffix("s")