Add test to verify re-exported auxiliary types

[GideonBature]

In order to address the issue in #137 to ensure that re-exported types auxiliary types are correct, I simply added a standalone test file where I defined a macro to assert that fields of re-exported types are of the expected auxiliary types.

This is still a WIP, still need to know if doing something like this aligns with the project and if I am on the right course before I continue...

[tcharding]

To review this I asked myself:

1. What are we trying to prove?
2. What does the integration_test/tests/aux_export.rs file prove
3. How do I know we didn't miss any of the auxiliary types?
4. When we add a newtype that has an auxiliary type what will stop us from forgetting to test it i.e., does this new file add any protection against forgetting?

If you ask your self these questions perhaps you can come up with the same review I would give?

[GideonBature]

To review this I asked myself:

1. What are we trying to prove?
2. What does the integration_test/tests/aux_export.rs file prove
3. How do I know we didn't miss any of the auxiliary types?
4. When we add a newtype that has an auxiliary type what will stop us from forgetting to test it i.e., does this new file add any protection against forgetting?

If you ask your self these questions perhaps you can come up with the same review I would give?

I see, thank you for these questions, I will look into 3 and 4 and come up with a better solution.