Expose individual components of UniquePortId in CXX API

[orecham]

Brief feature description

The UniquePortId is made up of components:

    pub struct UniqueSystemId {
        pid: u32,
        seconds: u32,
        nanoseconds: u32,
        counter: u32,
    }

An API to access these individual elements, in addition to all of the bytes making up the ID, should be added.