[FIX] mrp: `qty_available` computation of a kit and its component

When `qty_available` was being called
for a kit and its components at the same time,
e.g.:
 - Kit product
   - Product 1
   - Product 2

The kit product available qty was always computed to `0.0`,
because when computing its component available quantity,
they were computed to `0.0` because they were marked
as `protected` by the ORM when calling the compute method
for these records at the first call.
When the `qty_available` compute method for the kit
then called recursively the `qty_available` compute
method for the component, as the component record
were marked as protected,
the ORM filled their value with the Falsy value `0.0`.

This issue occured particularly in the upgrade integrity unit test
which makes sure the available quantities of the products remain
unchanged after upgrade. This test computes the available
quantities for a bunch of products at the same time,
and its therefore likely a kit product gets its available
quantity computed as the same time than its components.

upg-3185
upg-4215
upg-4228
upg-5558
upg-5745
upg-5856
upg-6012
upg-6064
upg-6076
upg-6306
upg-6514
upg-6588
upg-6729

closes odoo/odoo#65751

X-original-commit: 8e152a56
Signed-off-by: Arnold Moyaux <amoyaux@users.noreply.github.com>
Signed-off-by: Denis Ledoux (dle) <dle@odoo.com>