This change reorganizes existing automated tests into a clearer legacy test structure. It does not change business features directly, but helps maintain the test suite and supports smoother future development.

Follow-up of the homonymous community pull request.

Community: https://github.com/odoo/odoo/pull/129868

The tax reminder functionality has been folded into the main account reporting module to simplify maintenance. This cleanup keeps the same business capability while reducing separate module overhead and making future updates easier to manage.

We added the account_reports_tax_reminder module in stable, this pr will do some cleaning by merging the module in account_reports.

task: 3583207