fix: collect frontend dependencies of dev tools message handlers (CP: 24.10) (#25097)

FrontendDependencies resolves DevToolsMessageHandler subtypes to add
them as internal entry points, but the class was missing from the
`@HandlesTypes` of DevModeStartupListener. DevModeClassFinder only knows
the classes listed there and throws for anything else, and that
exception was swallowed by the surrounding catch block intended for a
missing dev tools classpath entry. As a result, frontend dependencies
declared by dev tools plugins were silently skipped in development mode
when the byte-code scanner is enabled.

Author: mcollovati

vaadin-dev-server/src/main/java/com/vaadin/base/devserver/startup/DevModeStartupListener.java

@@ -18,6 +18,7 @@
 
 import org.slf4j.LoggerFactory;
 
+import com.vaadin.base.devserver.DevToolsMessageHandler;
 import com.vaadin.flow.component.Component;
 import com.vaadin.flow.component.ComponentUtil;
 import com.vaadin.flow.component.Tag;
@@ -62,7 +63,8 @@
         JavaScript.Container.class, Theme.class, NoTheme.class,
         HasErrorParameter.class, PWA.class, AppShellConfigurator.class,
         Template.class, LoadDependenciesOnStartup.class,
-        TypeScriptBootstrapModifier.class, Component.class, Layout.class })
+        TypeScriptBootstrapModifier.class, DevToolsMessageHandler.class,
+        Component.class, Layout.class })
 @WebListener
 public class DevModeStartupListener
         implements VaadinServletContextStartupInitializer, Serializable,

vaadin-dev-server/src/test/java/com/vaadin/base/devserver/startup/DevModeClassFinderTest.java

@@ -19,6 +19,7 @@
 
 import jakarta.servlet.annotation.HandlesTypes;
 
+import com.vaadin.base.devserver.DevToolsMessageHandler;
 import com.vaadin.base.devserver.startup.DevModeInitializer.DevModeClassFinder;
 import com.vaadin.flow.component.Component;
 import com.vaadin.flow.component.WebComponentExporter;
@@ -64,7 +65,7 @@ public void applicableClasses_knownClasses() {
                 HasErrorParameter.class, PWA.class, AppShellConfigurator.class,
                 Template.class, LoadDependenciesOnStartup.class,
                 Component.class, TypeScriptBootstrapModifier.class,
-                Layout.class);
+                DevToolsMessageHandler.class, Layout.class);
 
         for (Class<?> clz : classes) {
             assertTrue("should be a known class " + clz.getName(),