Define strategy for Message Handling Components when several handlers for same `QualifiedName` are subscribed

[MateuszNaKodach]

Enhancement Description

Define what should happen (or should it be checked on boot time?) if someone define many handlers for same Command/Query/Event in the HandlingComponent.
The SimpleCommandBus and SimpleQueryBus throw a DuplicateCommandHandlerSubscriptionException and DuplicateQueryHandlerSubscriptionException respectively at this moment. Perhaps the message handling components should too?

Current Behaviour

Now it's possible and there is no exception.

Wanted Behaviour

To be defined.

Possible Workarounds

[smcvb]

Tying this issue to #3783, as I anticipate we can resolve both in one fell swoop.