Migrate to VerticleBase in module examples

See vert-x3/issues#649

There still are some examples with AbstractVerticle, but they don't need to migrated: either the start method is synchronous or pseudo-synchronous (virtual threads).

Signed-off-by: Thomas Segismont <tsegismont@gmail.com>

Author: tsegismont

vertx-core/src/main/asciidoc/index.adoc

@@ -322,15 +322,15 @@ will automatically stop any running server when the verticle is un-deployed.
 
 === What happened to Vert.x 4 Verticle and AbstractVerticle contracts?
 
-The contract defined by `Verticle` and `AbstractVerticle` was not adapted anymore to Vert.x 5 future based model
+The contract defined by `Verticle` and `AbstractVerticle` wasn't convenient anymore with Vert.x 5 future based model:
 
 [source,java]
 ----
 {@link examples.CoreExamples#verticleContract}
 ----
 
-`Verticle` and `AbstractVerticle` are not deprecated in Vert.x 5 and it is fine to use them, however it is not the default
-recommended choice anymore.
+Nevertheless, `Verticle` and `AbstractVerticle` are not deprecated in Vert.x 5.
+It is fine to use them, however it is not the default recommended choice anymore.
 
 === Verticle Types
 

vertx-core/src/main/java/examples/NetExamples.java

@@ -12,7 +12,10 @@
 package examples;
 
 import io.netty.handler.logging.ByteBufFormat;
-import io.vertx.core.*;
+import io.vertx.core.DeploymentOptions;
+import io.vertx.core.Future;
+import io.vertx.core.VerticleBase;
+import io.vertx.core.Vertx;
 import io.vertx.core.buffer.Buffer;
 import io.vertx.core.http.ClientAuth;
 import io.vertx.core.http.HttpServer;
@@ -172,20 +175,20 @@ public void example10(NetSocket socket) {
 
   public void example11(Vertx vertx) {
 
-    class MyVerticle extends AbstractVerticle {
+    class MyVerticle extends VerticleBase {
 
       NetServer server;
 
       @Override
-      public void start() throws Exception {
+      public Future<?> start() {
         server = vertx.createNetServer();
         server.connectHandler(socket -> {
           socket.handler(buffer -> {
             // Just echo back the data
             socket.write(buffer);
           });
         });
-        server.listen(1234, "localhost");
+        return server.listen(1234, "localhost");
       }
     }