When update_pot() was replaced with the global elecstate::update_pot() function, this TDDFT-specific saving logic was lost, causing all RT-TDDFT tests to fail.

This is a little bit tricky because we needed to find a way to preserve the TDDFT-specific save2 functionality (which handles Hamiltonian storage). The challenge was that only TDDFT solvers require this additional saving step, but we need to call it from the common iter_finish method in the base ESolver_KS class.

I have (temporarily) completed the call to the save2 function through the following scheme, and I am currently unaware of whether there is a better solution:

LGTM