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

core/builtins/src/kotlin/PropertyMetadata.kt

@@ -16,13 +16,7 @@
 
 package kotlin
 
-/**
- * Represents a property in a Kotlin class.
- */
-@Deprecated("Please use KProperty instead.", ReplaceWith("KProperty<*>", "kotlin.reflect.KProperty"))
-public interface PropertyMetadata {
-    /**
-     * The name of the property.
-     */
-    public val name: String
+@Deprecated("Please use KProperty instead.", ReplaceWith("KProperty<*>", "kotlin.reflect.KProperty"), DeprecationLevel.ERROR)
+internal interface PropertyMetadata {
+    val name: String
 }

core/builtins/src/kotlin/reflect/KProperty.kt

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+@file:Suppress("DEPRECATION_ERROR", "EXPOSED_SUPER_INTERFACE", "INVISIBLE_REFERENCE", "INVISIBLE_MEMBER") // for PropertyMetadata inheritance
 package kotlin.reflect
 
 /**