Feature: support init_chg dm to restart with DMR

[dyzheng]

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 #6652

Restart SCF from DMR is better than textfile of charge density in above test.

Unit Tests and/or Case Tests for my changes

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

What's changed?

• Example: My changes might affect the performance of the application under certain conditions, and I have tested the impact on various scenarios...

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 ...

[mohanchen]

You can check #6744, I have done some refators.

[mohanchen]

There are some failed tests

[mohanchen]

Do you want to further update the documents? @dyzheng