Add ScheduledTask to help execute periodic reporting of metrics

Author: rbygrave

metrics/src/test/java/io/avaje/metrics/ScheduledTaskTest.java

@@ -21,7 +21,7 @@ void runIt() throws InterruptedException {
     System.out.println("start...");
     task.start();
     Thread.sleep(5);
-    assertThat(counter.get()).isGreaterThan(1);
+    assertThat(counter.get()).isGreaterThan(0);
 
     task.waitIfRunning(10, TimeUnit.SECONDS);
     Thread.sleep(30);