Fix several restart issues

Description

For moving ions, the density and potential was not correctly recomputed after setting the ionic positions. Moreover, the force from the previous timestep was not dumped and loaded, such that the Verlet propagation of the ions showed differences after restarting.

The accuracy of the data written and read back in for the coordinates and also for the occupations was not high enough to get binary identical results.

To be changed in a separate MR: use the occupations as found in the restart data by setting RestartFixedOccupations to true by default. This should be the default behavior for restarting. This is not done here to disentangle the failing tests due to this change.

To be improved: the data for the coordinates and occupations should be written to binary files in the restart folder, which is not yet the case.

News snippet

Fix restart issues

Checklist

• I have checked that my code follows the Octopus coding standards