expensive check in EventUtil#checkEventBindings

#checkEventBindings needs to do a check for the tck.
however, we can do the same check (once) during bootstrapping before adding an observer.

reason why we don't need this runtime check here:
if an invalid event (with an invalid qualifier) is used in a dyn. #fire, we can ignore the invalid literal-instance because there is no corresponding observer (qualifiers of the observers would be checked during bootstrapping -> the startup would fail, if there is such an invalid observer).

-> we just need the qualifier-check during bootstrapping and a workaround that this (broken) tck-test still passes.