Before when we do `reserved(records)`, it iterates in a reverse
order of `records`. Unfortunately, the `__reserved__` method don't
exist explicitly in BaseModel then Python fallback on
its own implementation using `__getitem__` and `__len__` (coming from Sequence): https://github.com/python/cpython/blob/3.10/Lib/_collections_abc.py#L1047-L1049
Because it uses __getitem__, it breaks the prefetch of the recordset.
Example:
-------------
```
partners = self.env['res.partner'].browse(1, 2, 3, 4, 5)
for partner in reversed(partners):
partner.name
```
will generate 5 SQL requests to fetch data (one by record)
Then create our own `__reversed__` and handle the prefetch correctly
(like `__iter__`). Now in the example it will correctly generate only
1 SQL request because of the prefetch.
task-2687953
closesodoo/odoo#79622
Signed-off-by: Raphael Collet <rco@odoo.com>
Co-authored-by: rco-odoo <rco@odoo.com>
