TST: Add tests for internal EOF in read_csv
Title is self-explanatory.  Closes #5500.

## [Current coverage](https://codecov.io/gh/pydata/pandas/pull/14069?src=pr) is 85.27% (diff: 100%)

> Merging [#14069](https://codecov.io/gh/pydata/pandas/pull/14069?src=pr) into [master](https://codecov.io/gh/pydata/pandas/branch/master?src=pr) will decrease coverage by **<.01%**

``` diff
@@             master     #14069   diff @@
==========================================
  Files           139        139          
  Lines         50455      50455          
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
- Hits          43026      43025     -1   
- Misses         7429       7430     +1   
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [6645b2b...8c4cf85](https://codecov.io/gh/pydata/pandas/compare/6645b2b11a82343e5f07b15a25a250f411067819...8c4cf85943e647cbb8a0e081ad1e6277dbd309b9?src=pr)
 thanks!
