Make PropertyMetadata internal and deprecated with error

To make them inaccessible from Kotlin sources and drop them later. They're
still needed in runtime because Kotlin tests run old IDEA code (which depends
on PropertyMetadata) with our own runtime

compiler/testData/builtin-classes.txt

@@ -1084,7 +1084,7 @@ public abstract class Number {
     public abstract override /*1*/ /*fake_override*/ fun iterator(): kotlin.Iterator<N>
 }
 
-@kotlin.Deprecated(message = "Please use KProperty instead.", replaceWith = kotlin.ReplaceWith(expression = "KProperty<*>", imports = {"kotlin.reflect.KProperty"})) public interface PropertyMetadata {
+@kotlin.Deprecated(level = DeprecationLevel.ERROR, message = "Please use KProperty instead.", replaceWith = kotlin.ReplaceWith(expression = "KProperty<*>", imports = {"kotlin.reflect.KProperty"})) internal interface PropertyMetadata {
     public abstract val name: kotlin.String
         public abstract fun <get-name>(): kotlin.String
 }