[ADD] base_vat: VAT check for Venezuela

The current VAT check doesn't pass for valid Venezuelan VAT numbers (RIF). Venezuela has a specific method to validate their RIF, very different from the standard VIES check.

This commit adds an implementation of the VAT number validation in Venezuela. The validation is based on
(1) pattern matching
(2) checksum validation

Task id=3094593

closes odoo/odoo#107658

Signed-off-by: Florian Gilbert (flg) <flg@odoo.com>