Refactor: hs file output

[goodchong]

Reminder

• Have you linked an issue with this pull request?
• Have you added adequate unit tests and/or case tests for your pull request?
• Have you noticed possible changes of behavior below or in the linked issue?
• Have you explained the changes of codes in core modules of ESolver, HSolver, ElecState, Hamilt, Operator or Psi? (ignore if not applicable)

Linked Issue

Fix #6837

Unit Tests and/or Case Tests for my changes

• A unit test is added for each new feature or bug fix.

What's changed?

• Extended out_mat_hs2 to map integers 0 to 4 (disabled, single-file text/binary, and multi-file text/binary).
• Maintained backward compatibility with string boolean inputs ('true', 'false', 'yes', 'no').
• Added support for rank suffixes (.0, .1, etc.) for multi-file CSR and position matrix outputs when reduce is false.
• Refactored output_HSR to use a clean templated loop structure, eliminating duplicate code blocks.
• Optimized parallel CSR output performance using in-memory collective MPI gathering (MPI_Gatherv), replacing slow disk-based row-by-row gathering.

Any changes of core modules? (ignore if not applicable)

• Example: I have added a new virtual function in the esolver base class in order to ...