Output partial charge density of a specific iband list

[gawcista]

Background

In current version, the partial charge can be obtained with calculation=get_pchg. However, the set of nbands_istate output too many unexpected result if one just want pchg with several specific band index.

Describe the solution you'd like

It is suggested to provide a keyword i.e. iband to determine a band index list. Only these wave functions are calculated. Similar tag can be found in VASP as IBAND: https://www.vasp.at/wiki/index.php/IBAND

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.

[WHUweiqingzhou]

Thanks to @wenfei-li, PR #3501 enables ABACUS can output partial charge density of a specific iband list in PW basis.

[AsTonyshment]

Closed by #3934.