[FIX] stock: replenish report in 3 months

Currently the replenishment report look for forecasted quantity of
product today. It means that for a product if the delivery is planned
for today the forecast will be -1, at j-1 it will be 0. However for the
majority of use case, products take days to order and arrive.

Example:
- Product A, purchase delivery time 5 days.
- You are the 01-01-2021 and create a SO for 10-01-2021
Currently:
- Product will appear in the replenishment report the 10-01-2021 and
you will receive it the 15-01-2021. So you are late to deliver your
customer.
Desired behavior:
- Product appear in the replenishment report the 05-01-2021 and if you
order it directly you will receive it the 10-01-2021.

If you want to have more time to deliver than one day, security lead
time are there for it.

However the usecase like:
Product arrive in 2 months and you receive it in 3 days, the product won't
appear in the replenish report anymore since the forecast in 3months is
0

It could happens that more product are missing in 3 months than today,
so the system could have more delivery lead times and forecast at date
to compute -> be slower. In that case a parameter could be
added to skip the delivery times computation for each product/warehouse
and just display the forecast in 3 months and let user compute their
schedule themself.

closes odoo/odoo#73652

Signed-off-by: Arnold Moyaux <amoyaux@users.noreply.github.com>