Make concrete message_passing implementation public

[NEOatNHNG]

The alias alone is not usable from other modules.

[LittleHuba]

Closing this, as visibility was extended appropriately for other S-CORE modules to access the concrete targets.
Making this publicly visible is not intended, since this is a library not intended for users of S-CORE.

[NEOatNHNG]

We have other use cases in infrastructure components apart from logging where we would like to re-use the message passing. I mean it is OK if we don't want S-CORE applications to use message passing directly, but other infrastructure components should be fine. Similar argument could be made for shared_memory from baselibs. We also don't want applications to use that directly but we don't limit the visibility there either.

Most current example is the someip gateway where @lurtz is working on a bridge implementation which would also need to access message_passing. But we have also ETAS-internal use cases for this. @mishraajitesh

[LittleHuba]

@NEOatNHNG could you please give some insight into the ETAS-internal use cases?
This would help us tremendously in our evaluation.
Currently, the agreement in S-CORE is that all communication between applications shall happen via mw::com.
If you have a valid use case for directly relying on message_passing, we should reopen that discussion.