8236695: java.lang.Record should be declared with an explicit constructor

Reviewed-by: psandoz, chegar

src/java.base/share/classes/java/lang/Record.java

@@ -90,6 +90,11 @@ package java.lang;
 @jdk.internal.PreviewFeature(feature=jdk.internal.PreviewFeature.Feature.RECORDS,
                              essentialAPI=true)
 public abstract class Record {
+    /**
+     * Constructor for record classes to call.
+     */
+    protected Record() {}
+
     /**
      * Indicates whether some other object is "equal to" this one.  In addition
      * to the general contract of {@link Object#equals(Object)},