Discover all VaadinServiceInitListener beans in QuarkusInstantiator

[mcollovati]

QuarkusInstantiator collects VaadinServiceInitListener by:

• delegating to the DefaultInstantiator, that uses ServiceLoader
• registering a listener that fires a CDI ServiceInitEvent event, to engage all observer methods

However, beans implementing VaadinServiceInitListener are not considered.
Currently, this could be an issue in @QuarkusTest, if you, for example, want to use a custom QuarkusTestProfile to define a bean that does some initialization stuff, but for a couple of tests.
If you define a class with an @Observes method, it will be invoked for all tests.

There are workaround (e.g. use @IfBuildProfile annotation on the observer class, or define the method as @Observes(notifyObserver = Reception.IF_EXISTS) and inject the bean into the test class to force the creation), but it would be easier if QuarkusInstantiator also collects all beans implementing VaadinServiceInitListener so that a developer could simply define the bean in the test profile.

Probably should only load VaadinServiceInitListener beans having the @VaadinServiceEnabled qualifier