`UnusedMethod` marks CDI observer methods as unused

CDI observer methods have a method parameter annotated with (using the jakarta namespace) `jakarta.enterprise.event.Observes` or `jakarta.enterprise.event.ObservesAsync` for synchronous or asynchronous event observation respectively.

`UnusedMethod` only ignores methods that annotated with selected annotation like e.g. `jakarta.annotation.PostConstruct` and others.

As such these CDI observer methods will be marked as unused and produce a warning.