Draft: Try to avoid misleading constness in Extrapolator

This re-surfaced due to a comment in my last MR on this codebase from @jojungge , where unique_ptr was introduced as return argument

I assume here that ObjContainer will also be improved by @sroe so this might help us a bit more. He is in the process of expanding the test coverage for this code .

If this does what is advertises then can rm the const from the std::unique_ptr<const Trk::Parameters> and have a proper factory return of std::unique_ptr<Trk::Parameters>, currently we pass full "ownership" but then we force clients to clone or const_cast in order to modify what they own ...

There are some internal clones extra, which we will need to regain client side (hopefully as this is I assume @jojungge wants) or by @sroe efforts.