BUG: Multiline Eval broken for local variables after first line
Also fixes the code which attempted to ignore any blank lines in the
multiline expression.

 - [x] closes #15342 
 - [x] tests added / passed
 - [x] passes ``git diff upstream/master | flake8 --diff``
 - [x] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/15343?src=pr&el=h1) Report
> Merging [#15343](https://codecov.io/gh/pandas-dev/pandas/pull/15343?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/d38d142aaac5ee046aabc32c1e6422f86c37dc41?src=pr&el=desc) will **decrease** coverage by `-0.01%`.


```diff
@@            Coverage Diff             @@
##           master   #15343      +/-   ##
==========================================
- Coverage   86.32%   86.32%   -0.01%     
==========================================
  Files         141      141              
  Lines       51163    51162       -1     
==========================================
- Hits        44167    44166       -1     
  Misses       6996     6996
```


| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/15343?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/computation/eval.py](https://codecov.io/gh/pandas-dev/pandas/compare/d38d142aaac5ee046aabc32c1e6422f86c37dc41...fe67ede5abed071980a44600e66397a41577780d?src=pr&el=tree#diff-cGFuZGFzL2NvbXB1dGF0aW9uL2V2YWwucHk=) | `94.56% <100%> (-0.06%)` | :x: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/15343?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/15343?src=pr&el=footer). Last update [d38d142...fe67ede](https://codecov.io/gh/pandas-dev/pandas/compare/d38d142aaac5ee046aabc32c1e6422f86c37dc41...fe67ede5abed071980a44600e66397a41577780d?el=footer&src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments). @chris-b1  Thanks @stephenrauch - I only half remember how the scope level works - is there any way to make this clearer / cleaner?  We're now doing a `+1` in 3 places.

https://github.com/stephenrauch/pandas/blob/c7ac553366d747d33fba861e6f3afcc44f145721/pandas/computation/eval.py#L257

https://github.com/stephenrauch/pandas/blob/c7ac553366d747d33fba861e6f3afcc44f145721/pandas/computation/scope.py#L22

https://github.com/stephenrauch/pandas/blob/c7ac553366d747d33fba861e6f3afcc44f145721/pandas/computation/scope.py#L102
 @chris-b1 , so yesterday was the first time I had seen this code base, so I am not familiar with the workings of the scope levels.  I did see all of the +1's, and thought it note-worthy, but didn't investigate any further. Looked at this again, and I'm fine with your fix.  `level` is ultimately passed to `sys._getframe`, so makes sense that we keep incrementing as we go down the call stack. thanks @stephenrauch !