Added keyboard shortcuts (hotkeys) to the VAT return report submission buttons to meet WCAG AA accessibility standards. This improvement ensures that users can now submit VAT returns using keyboard navigation, making the system more accessible to all users including those with mobility limitations.

In order to be compliant with WCAG AA norms, some buttons weren't accessible with the keyboard for the submission of the VAT return report.

task-3631625

Forward-Port-Of: odoo/enterprise#53218