Make Ref classes for shared vars Serializable

#KT-14566 Fixed

core/runtime.jvm/src/kotlin/jvm/internal/Ref.java

@@ -16,10 +16,12 @@
 
 package kotlin.jvm.internal;
 
+import java.io.Serializable;
+
 public class Ref {
     private Ref() {}
 
-    public static final class ObjectRef<T> {
+    public static final class ObjectRef<T> implements Serializable {
         public T element;
 
         @Override
@@ -28,7 +30,7 @@ public class Ref {
         }
     }
 
-    public static final class ByteRef {
+    public static final class ByteRef implements Serializable {
         public byte element;
 
         @Override
@@ -37,7 +39,7 @@ public class Ref {
         }
     }
 
-    public static final class ShortRef {
+    public static final class ShortRef implements Serializable {
         public short element;
 
         @Override
@@ -46,7 +48,7 @@ public class Ref {
         }
     }
 
-    public static final class IntRef {
+    public static final class IntRef implements Serializable {
         public int element;
 
         @Override
@@ -55,7 +57,7 @@ public class Ref {
         }
     }
 
-    public static final class LongRef {
+    public static final class LongRef implements Serializable {
         public long element;
 
         @Override
@@ -64,7 +66,7 @@ public class Ref {
         }
     }
 
-    public static final class FloatRef {
+    public static final class FloatRef implements Serializable {
         public float element;
 
         @Override
@@ -73,7 +75,7 @@ public class Ref {
         }
     }
 
-    public static final class DoubleRef {
+    public static final class DoubleRef implements Serializable {
         public double element;
 
         @Override
@@ -82,7 +84,7 @@ public class Ref {
         }
     }
 
-    public static final class CharRef {
+    public static final class CharRef implements Serializable {
         public char element;
 
         @Override
@@ -91,7 +93,7 @@ public class Ref {
         }
     }
 
-    public static final class BooleanRef {
+    public static final class BooleanRef implements Serializable {
         public boolean element;
 
         @Override