Feature: autoset efield related parameters

[YuLiu98]

Linked Issue

Fix #3386

What's changed?

• Autoset efield_pos_max and efield_pos_dec according to the vacuum region. Specifically, efield_pos_dec is auto-set to one-tenth of the vacuum width, efield_pos_max is auto-set to the center of the vacuum region minus one-twenty of the vacuum width

[kirk0830]

Thanks for your effort on autoset on dipole correction, this will make ABACUS more user-friendly than before. However, I also leave some comments, please find them and add some explanations accordingly, thanks!

[kirk0830]

This PR enables the autoset of dipole correction, so that user can pay less attention to finding proper parameter for related parameters.

Strictly speaking, this implemented strategy works for static (SCF) calculation but needed to evaluate and widely test for relax cases.
Comparatively in corresponding fixed issue, there is another strategy, in which the minima of charge density averaged on plane whose norm vector is parallel with user-defined direction, is found first and the coordinate is added by half of cell length in that direction, such a position is assumed as center of charge of cell: