Add real MySQL and PostgreSQL coverage for ORM query and relationship test suites

[techmahedy]

This PR upgrades Doppar’s unit test setup toward a more industry-standard multi-driver structure. It introduces shared driver-aware test harnesses so the same ORM and relationship behavior can run against:

1. sqlite
2. mysql
3. pgsql

What Changed

• extracted large SQLite-only ORM query suites into shared behavior files
• added concrete driver wrappers for:
  • model query suites
  • relationship suites
  • selected builder relationship suites
• added reusable driver-aware test bases for live PDO-backed tests

updated GitHub Actions to:

• keep normal Linux/Windows jobs fast by excluding external DB groups
• add a dedicated Ubuntu job that runs real MySQL and PostgreSQL suites