[FIX] mrp: print bomstructure report with float quantity

Usecase to reproduce (chrome):
- Create a BoM with float quantity in component
- Print the BoM cost and structure report

When using a type="number" on firefox it is not possible to use a
decimal. However on chrome there is no restriction and a decimal
could be use. It makes senses to be able to work with decimal
(e.g. the UoM is in kg)

It also exists an explicit cast to integer since data are received as
string from the javascript. However since quantity displayed could be
decimal, the cast should be adapted to float.

Closes #27464
Fixes #27437

closes odoo/odoo#27522