[IMP] hr_skills*: Add certification and course in employee profile

When a employee succeed a course or a certification, a new line
will be added in resumé of employee profile.

+ [FIX] hr_skills: remove sequence to sort resumé

Actually, sorting a resumé doesn't work because we add new line for
title in the array.

With this commit, all sequence are removed. The resumé is sorted
by date and skills are sorted by level.

closes odoo/odoo#31764

Signed-off-by: Yannick Tivisse (yti) <yti@odoo.com>