Automatically add padding to `FullGridCellList` bounding box?

When a particle is in a boundary cell of the grid, it is not surrounded by cells, so we get an out-of-bounds exception when looking for neighbor cells. Currently, one has to manually add a padding of `search_radius` to the bounding box. I think it would be better if the padding was automatically included (only when not using periodicity?) and maybe could be deactivated with `padding = false`.