Improve output of H and S matrices: output matrices when the self-con…

[LiuXiaohui123321]

…sistent iteration steps reach scf_nmax, even if the charge density doesn't converge.

Reminder

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Linked Issue

Fix #4093

On top of the current code framework, I just simply add the output H and S matrices when the self-consistent iteration steps reach scf_nmax. However, I'm not quite sure if this will have an impact on the rest of the update_pot() function, which contains both the function to output the H and S matrices and a few other functions as well. Also, I think the function update_pot() is a bit unclear in its functionality.