TST: Add new test for flaky usecols
Title is self-explanatory.

xref #14984.
Closes #13604.
## [Current coverage](https://codecov.io/gh/pandas-dev/pandas/pull/15051?src=pr) is 84.75% (diff: 100%)
> Merging [#15051](https://codecov.io/gh/pandas-dev/pandas/pull/15051?src=pr) into [master](https://codecov.io/gh/pandas-dev/pandas/branch/master?src=pr) will not change coverage

```diff
@@             master     #15051   diff @@
==========================================
  Files           145        145          
  Lines         51146      51146          
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
  Hits          43350      43350          
  Misses         7796       7796          
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [6eb705f...f59565c](https://codecov.io/gh/pandas-dev/pandas/compare/6eb705f5350a0eeffd9e7663d7b4bf54acb4d6af...f59565c3daaf2e34d1b4e6d6e17bbbaf998678ca?src=pr)