[IMP] eLearning: adds course and certification stat button on partner

Adds two stats button on res.partner form view :
- The first one will show all the courses that the partner is following.
- The second one will show all the certifications the partner has passed.
When the partner is a company :
- All the courses followed by all the partners are shown without duplicate.
- All the certifications passed by all the partners are shown.

PR : #34908
Task ID : 2034097

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>