[FIX] point_of_sale: Multicompany tax

Steps to reproduce the bug:

- Create a multi-company environment with two companies A & B
- Create two sales taxes TA & TB, one for company A & one for company B
- Created a shared product P and assign both TA & TB
- Create a fiscal position FP that maps TA and TB to other taxes
- Login with user having access of both companies
- Enable a POS session S with fiscal position and select FP
- Open S and select P as product

Bug:

A traceback was raised

PS: Only the taxes of company's user are loaded in taxes_by_id
So when trying to fetch taxes from a product with function get_taxes,
the taxes from other companies than company's user must be ignored.

opw:2448785

closes odoo/odoo#66684

Signed-off-by: Simon Goffin (sig) <sig@openerp.com>