simulate all package manager actions explicitly

simulate all package manager actions explicitly

If a planner lets actions to be figured out by dpkg in pending calls
these actions aren't mentioned in a simulation. While that might be
a good thing for debugging, it would be a change in behavior and
especially if a planner avoids explicit removals could be confusing for
users. As such we perform the same 'trick' as in the dpkg implementation
by performing explicitly what would be done by the pending calls.

To save us some work and avoid desyncs we perform a layer violation by
using deb/ code in the generic simulation – and further we perform ugly
dynamic_cast to avoid breaking the ABI for nothing; aptitude is the only
other user of the simulation class according to codesearch.d.n and for
that our little trick works. It just isn't working if you happen to
extend pkgSimulate or otherwise manage to call the protected Go methods
directly – which isn't very realistic/practical.