The India localization test suite now uses a shared setup for common test data used across multiple tax report checks. This reduces duplicated work in the codebase and helps make future changes to India reporting tests faster and more consistent, without changing user-facing behavior.

Because a lot of indian test cases create similar fields and functions this commit creates a common test class that sets up the bulk of data needed for all indian test cases.

- Task: 3892508
- [Community PR](https://github.com/odoo/odoo/pull/167991)