This is a bit of a cheat of a refactoring that simply extracts the logic for collecting a column's attributes out of `get_schema_info` and into its own method (`get_attributes`).

I found that in PRs like #779 that the Rubocop ABC limit was being exceeded:

```
lib/annotate/annotate_models.rb:235:5: C: Metrics/AbcSize: Assignment Branch Condition size for get_schema_info is too high. [145/145]
    def get_schema_info(klass, header, options = {}) ...
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```

Hopefully, this should break this up and reduce the complexity of the method.

There are opportunities to go further, but I thought this could be a good place to start. 

I would be open and interested in discussing further refactoring opportunities if it would make sense (maybe creating some new classes to encapsulate some of this logic).