8326389: [test] improve assertEquals failure output

Backport-of: 9b1f1e5294e130ec444b08af1f73d08e86fd91ee

Author: GoeLin

test/lib/jdk/test/lib/Asserts.java

@@ -201,10 +201,7 @@ public static void assertEquals(Object lhs, Object rhs) {
      */
     public static void assertEquals(Object lhs, Object rhs, String msg) {
         if ((lhs != rhs) && ((lhs == null) || !(lhs.equals(rhs)))) {
-            msg = Objects.toString(msg, "assertEquals")
-                    + ": expected " + Objects.toString(lhs)
-                    + " to equal " + Objects.toString(rhs);
-            fail(msg);
+            fail((msg == null ? "assertEquals" : msg) + " expected: " + lhs + " but was: " + rhs);
         }
     }