[HOTFIX] - Fix application of column operations within TableOperation

[joshmcrae]

This PR adds more comprehensive tests for TableOperation and fixes some bugs with the application of column operations when altering tables. Specifically, the following scenarios were identified and fixed:

1. Applying the addition of a column to the dropping of same column (now results in a column modification)
2. Applying the modification of a column to any operation on that same column uses the original column name (instead of the new name if renamed)
3. Applying the change of a column to any column operation on the same column uses that column's original name. In the case of an add, we clean up the new_name option on the column operation since it is not relevant.

[Glenn-Ewing]

I did not pull this down to run things locally, but code changes look sane, and tests look like they cover the changes made.
Let me know if you'd prefer I pull and run locally, but short of that, these look like great enhancements, thanks @joshmcrae !