Steps to reproduce:
-------------------
1. create a new database with industry_fsm_sale_report, planning and no demo data;
2. enable debug mode;
3. go to settings;
4. load demo data.

Issue:
------
Fails to load demo data due because of a `KeyError` on
`planning.slot.allocated_hours`.

Cause:
------
When we update the module and instantiate the field, we will call _recompute_all method but the method _compute_planning_hours_planned of sale.order.line does an `add_to_compute` of planning.slot() field allocated_hours.

So after _recompute_all, there is still something to compute. Then we when we apply allocated_hours override (from sale_planning module) we change the field object:

```py from models.py Model._setup_base
if len(fields_) == 1 and fields_[0]._direct and fields_[0].model_name == cls._name:
   cls._fields[name] = fields_[0] # we reuse the field
else:
   Field = type(fields_[-1])
   self._add_field(name, Field(_base_fields=fields_)) # new reference
```

and when we do the recompute, it is going to be done with the old field reference that is now no longer on the model.

Solution:
---------
The issue comes from using add_to_compute inside a compute, in this particular case (order of compute, field that is overriden, module update that modify records/recompute values, ...) it is causing an issue.

So to avoid this issue, we force the recomputation directly after the add_to_compute.

Note:
-----
This is only happening in saas-16.4 and over because by chance, the _recompute_all in saas-16.3 and below recomputes
sale.order.line.planning_hours_planned before
planning.slot.allocated_hours. So by chance, when we add allocated_hours to be recomputed, it was already going to be done.

In saas-16.4 planning.slot.allocated_hours is computed before planning_hours_planned and so the _recompute_all still has something to compute after _recompute_all.

opw-3517083
opw-3691750

Closes odoo/odoo#139603

# note

There was another PR previously about this issue (https://github.com/odoo/odoo/pull/139603) but this one should more sharply fix the origin of the issue.

Forward-Port-Of: odoo/enterprise#57804