8325189: Enable this-escape javac warning in java.base

Reviewed-by: alanb, erikj, naoto, smarks, ihse, joehw, lancea, weijun

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

@@ -71,6 +71,7 @@ public class AssertionError extends Error {
      * @param detailMessage value to be used in constructing detail message
      * @see   Throwable#getCause()
      */
+    @SuppressWarnings("this-escape")
     public AssertionError(Object detailMessage) {
         this(String.valueOf(detailMessage));
         if (detailMessage instanceof Throwable)