Currently, there is a directy one to one relation between

 - DELAYED_ACTION_TYPE_REFRESH_ALL_*

 - REFRESH_ALL_TYPE_*

 - NMP_OBJECT_TYPE_*

For IP addresses, routes and routing policy rules, when we request
a refresh-all (NLM_F_DUMP), we want to specify the address family.

For addresses and routes that is currently solved by having two
sets of NMPObject types, for each address family one.

I think that is cumbersome because the implementations of both address
families are quite similar. By implementing both families as different
object types, we have a lot of duplicate code and it's hard to see where
the families actually differ. It would be better to have only one NMPObject
type, but then when we "refresh-all" such types, we still want to be able
to dump all (AF_UNSPEC) or only a particular address family (AF_INET, AF_INET6).

Decouple REFRESH_ALL_TYPE_* from NMP_OBJECT_TYPE_* to make that
possible.