control the output frequency of out_pot and out_chg

[Satinelamp]

Background

currenty we could output electrostatic potential at the last step of MD, we also need to output electrostatic potential at every step,

Describe the solution you'd like

Add an option to control the output frequency of out_pot like using out_freq_elec to control the output frequency of out_chg.

Task list only for developers

• [ ] Notice possible changes of behavior
• [ ] Explain the changes of codes in core modules of ESolver, HSolver, ElecState, Hamilt, Operator or Psi

Notice Possible Changes of Behavior (Reminder only for developers)

No response

Notice any changes of core modules (Reminder only for developers)

No response

Notice Possible Changes of Core Modules (Reminder only for developers)

No response

Additional Context

No response

Task list for Issue attackers (only for developers)

• [ ] Review and understand the proposed feature and its importance.
• [ ] Research on the existing solutions and relevant research articles/resources.
• [ ] Discuss with the team to evaluate the feasibility of implementing the feature.
• [ ] Create a design document outlining the proposed solution and implementation details.
• [ ] Get feedback from the team on the design document.
• [ ] Develop the feature following the agreed design.
• [ ] Write unit tests and integration tests for the feature.
• [ ] Update the documentation to include the new feature.
• [ ] Perform code review and address any issues.
• [ ] Merge the feature into the main branch.
• [ ] Monitor for any issues or bugs reported by users after the feature is released.
• [ ] Address any issues or bugs reported by users and continuously improve the feature.

[Satinelamp]

It seems the out_freq_elec is designed to output charge density at the chosen electronic steps, so we might use one parameter to control the behavior of out_chg and out_pot, so we could output charge density and electrostatic potential at desired ionic steps.