Centralize Arithmetic Tests
Lots of tests in tests.series.test_operators and tests.frame.test_operators that need to be split up, parametrized, and moved to the appropriate test_arithmetic module+class.  This handles the most obvious cases.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19471?src=pr&el=h1) Report
> Merging [#19471](https://codecov.io/gh/pandas-dev/pandas/pull/19471?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/d37d867cbb5665ef8cae1ff580fa377eccc84253?src=pr&el=desc) will **increase** coverage by `0.02%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/19471/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/19471?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #19471      +/-   ##
==========================================
+ Coverage    91.6%   91.62%   +0.02%     
==========================================
  Files         150      150              
  Lines       48724    48724              
==========================================
+ Hits        44632    44644      +12     
+ Misses       4092     4080      -12
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.99% <ø> (+0.02%)` | :arrow_up: |
| #single | `41.74% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/19471?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/19471/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `66.95% <0%> (+1.73%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19471?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/19471?src=pr&el=footer). Last update [d37d867...76d32df](https://codecov.io/gh/pandas-dev/pandas/pull/19471?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks!