Transactional processing changes in Micronaut 4

### Issue description

The tracking issue for changes expected to be in Micronaut 4:

- TX propagation should be rewritten using a new propagation API from Micronaut Core
- `@TransactionalAdvice` might need to be repeatable to allow different TX demarcation
- Transaction synchronization should be rewritten to be available on the transaction instance, not as a static state