Before this commit, the SQL query generated in `_get_aal_query` utilized a `LEFT JOIN` with a complex `OR` condition on the join clause: `(bl.company_id IS NULL OR bl.company_id = al.company_id)`.

Because this condition lacks a strict equality constraint, the planner cannot build a hash table for the join. Consequently, it is forced to fallback to a Nested Loop Join strategy, evaluating the condition as a filter for every row pair. This results in significant performance degradation on large datasets.

This commit optimizes the query by splitting the logic into two separate `SELECT` statements combined with a `UNION ALL`:
1. Matches where `company_id` is explicitly equal.
2. Matches where `company_id` is NULL.

By separating these conditions, the planner can now prioritize a Hash Join for the equality check and handle the NULL join separately, significantly reducing execution time.

References:
- Original PR introducing the logic: https://github.com/odoo/enterprise/pull/82955
- Plan Before (Join Filter): https://explain.dalibo.com/plan/a55476hgb73ea7g6#plan
- Plan After (Hash Cond): https://explain.dalibo.com/plan/3b9g484569a86efb#plan

opw-5460862

Forward-Port-Of: odoo/enterprise#104531
Forward-Port-Of: odoo/enterprise#104299

Issue:

When using negative amounts, for example to explicitly show a discount, the tax calculation is incorrect due to the application of the `abs` function. Furthermore, the way to find out if a tax is of the withholding type is based on the sign of the value, which can lead to error in these cases.

Cause:

A previous change (#237235) added the `abs` function so the 'TotalTaxesWithheld' would be always with positive value. But this also affects the calculation of taxes 'TotalTaxOutputs' in some cases, such as if the invoice line has negative values.

Steps to reproduce:

- Install `l10n_es_edi_facturae`
- With the ES company, create an invoice with some standard lines and one line with negative amounts, as an explicit discount
- Confirm the invoice and send (facturae)
- Open the XML attached in the chatter
- Observe that the taxes amounts (VAT and WITHHOLDING) are erroneous

A correct invoice should be for example:

```
Product        Price       Taxes       Amount
---------------------------------------------
PRODUCT-A       1000    21%VAT 15%WHI    1000
Discount        -100    21%VAT 15%WHI    -100
---------------------------------------------
                       Untaxed amount     900
                      Withholding 15%    -135
                              VAT 21%     189
                      -----------------------
                                 TOTAL    954
```

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