TST: Parametrize tests in tools/test_numeric.py
Title is self-explanatory.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/21717?src=pr&el=h1) Report
> Merging [#21717](https://codecov.io/gh/pandas-dev/pandas/pull/21717?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/8f322149ebd2a30f2f2d48c06863cd783166fa84?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/21717/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/21717?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #21717   +/-   ##
=======================================
  Coverage   91.92%   91.92%           
=======================================
  Files         158      158           
  Lines       49703    49703           
=======================================
  Hits        45689    45689           
  Misses       4014     4014
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.3% <ø> (ø)` | :arrow_up: |
| #single | `41.99% <ø> (ø)` | :arrow_up: |


------

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> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/21717?src=pr&el=footer). Last update [8f32214...3042714](https://codecov.io/gh/pandas-dev/pandas/pull/21717?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @jreback @jschendel : Comments addressed, and all is still green.  PTAL. thanks @gfyoung very nice!