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/util/Timer.java

@@ -178,6 +178,7 @@ public class Timer {
      * @throws NullPointerException if {@code name} is null
      * @since 1.5
      */
+    @SuppressWarnings("this-escape")
     public Timer(String name, boolean isDaemon) {
         var threadReaper = new ThreadReaper(queue, thread);
         this.cleanup = CleanerFactory.cleaner().register(this, threadReaper);