Feature: mixing density and magnetism {mx,my,mz} separately for non-colinear calculation

[WHUweiqingzhou]

Linked Issue

According to our roadmap for mixing method #3138
Fix #3285 for nspin=4

What's changed?

1. Mix density and magnetism {mx,my,mz} separately.
2. Kerker density and magnetism {mx,my,mz} separately.
3. Change default value of mixing_beta_mag and mixing_gg0_mag for nspin=4
4. update the reference date of 104_PW_NC_magnetic

Note:

1. In 104_PW_NC_magnetic, old mixing method give the total energy -5.866175e+03, while the new method can give a lower one -5.866197e+03. This mean old method fails to find the lowest state.
2. Default value mixing_beta_mag and mixing_gg0_mag is changed in this PR. Before this PR, the default value mixing_beta_mag=mixing_beta, mixing_gg0_mag=mixing_gg0. After this PR, the default value mixing_beta_mag=4*mixing_beta, mixing_gg0_mag=0.0.

[dyzheng]

This PR can improve the performance of mixing for NSPIN=4 cases.