Notification LegacyEventConverter should be defined for multiple types

XWIKI-17040 allows to now define some custom LegacyEventConverter to be able to reuse the storage parameters. However, those custom converters are defined by types only, the name of component being the supported type.
But we might have several events of the same application that would want to use the same LegacyEventConverter: in that case, it looks like a hack to use multiple names on the component to be able to reuse the component for the various.
Sounds like a better idea to implement a proper way to be able to define a LegacyEventConverter that support multiple types, like we do for RecordableEventConverter.