[Bug] - Clipping with ``states_at_boundary`` and a CHD/CNC package incorrectly broadcasts layer and time

[JoerivanEngelen]

Bug description
Another one @jdelsman run into:

Calling Modflow6Simulation.clip_box with the states_at_boundary and a ConstantHead or ConstantConcentration package with less layers (e.g. only assigned to layer 2 and 3) results in an inner alignment, whereas we need an outer alignment.

The same holds for the time domain, where some extra logic is required: In the filtering of cells already present in ConstantHead or ConstantConcentration , we want to forward fill the data of these packages in the cells, to properly filter cells already present in constant state packages from the states at boundary.