This commit adds 4 attachments to the Latvian tax report
and an XML export for the tax report (including the attachments).

The attachments are the following
- PVN 1-I: domestic purchase / import
- PVN 1-II: EU purchase
- PVN 1-III: domestic sales / export
- PVN 2: EU sale

The attachments give more details for the tax report.
The lines of the attachments are "transactions"
A "transaction" is identified by the move and the transaction type or document type.
The transaction type is given via a tax tag (see community PR).
- PVN 1-I: transaction type, move
  - Small transactions (< 150€) are aggregated separately under transaction types 'V' or 'T'
    independently of the move
  - 'V': All small transactions of a partner in case the total of all their small transactions reaches 150€
    - There is max 1 line per partner
  - 'T': All small transactions that are not grouped under some 'V' line
    - There is max 1 line like this; it has no partner information
- PVN 1-II: transaction type, move
  - Small transactions (< 150€) are aggregated separately under transaction types 'V' or 'T'
    (like PVN 1-I)
- PVN 1-III: document type, move and line in the main tax report
  - All transactions with (document) type 'X' are aggregated on a single line
  - Small transactions (< 150€) are aggregated separately under document types 'V' or 'T'
    (like PVN 1-I)
  - The line in the main tax report is ignored for 'X' and small transactions
- PVN 2: transaction type, move
  - No aggregation is performed here

Only account move lines that are tagged with a transaction type (1-I, 1-II, 2)
or a relevant tag for the main report (1-III) are shown in the reports.

The tags `Rep` and `C (car)` only take 40% and 50% respectively of the
base amounts. The tax amount is assumed to be split correctly.

task-4251184

Forward-Port-Of: odoo/enterprise#84135

This PR introduces support for electronic e-Resguardos for Uruguay, fully compliant with DGI regulations and integrated into the existing electronic invoicing flow via Uruware.

The implementation is based on the existing withholding framework from Ecuador, with references to Argentina’s approach, and includes the necessary adaptations to meet Uruguayan legal and functional requirements.

Key features included in this PR:

- Out-of-the-box availability: once the module is installed, users can create e-Resguardos without additional activation steps.
- Base configuration for withholdings:
  - Common withholding taxes (VAT and IRPF).
  - New field for DGI Withholding Code on taxes.
  - Configurable destination and default withholding accounts.
- Two main functional flows:
  - Creation of e-Resguardos from a single vendor bill.
  - Creation of e-Resguardos with multiple or no invoice references, including proper reference handling in XML depending on payment context.
- Automatic calculations of withheld amounts based on selected tax and base.
- XML generation and submission through the existing Uruware connection, including reception of validated XML (CAE) and PDF with electronic stamp.
- Compliance with the 10,000 UI threshold, enabling users to generate e-Resguardos when required by regulation.
- Storage and visualization of XML and PDF directly in Odoo, with printing support.
- Comprehensive testing coverage: single and multi-invoice cases, without reference, threshold logic, XML validation, and PDF rendering.

This PR lays the foundation for future extensions to additional e-Resguardo types while delivering a complete and compliant solution for the most common withholding scenarios in Uruguay.

Task: 4557347