Call init on delegate from TimedScheduler

The TimedScheduler class doesn't currently provide an override for the
`init()` method, which means it calls the default implementation on the
interface that delegates to `start()`. This works fine for most
schedulers, since they have a valid implementation of `start()`. However,
the newer BoundedElasticThreadPerTaskScheduler throws an error for
`start()`, so wrapping it in a TimedScheduler causes it to crash
immediately when `init()` gets called.

We should call the wrapped scheduler's `init()` method instead, which
allows users to get metrics for their virtual thread schedulers.

reactor-core-micrometer/src/main/java/reactor/core/observability/micrometer/TimedScheduler.java

@@ -135,6 +135,11 @@ public void start() {
 		delegate.start();
 	}
 
+	@Override
+	public void init() {
+		delegate.init();
+	}
+
 	static final class TimedWorker implements Worker {
 
 		final TimedScheduler parent;