Avoid unnecessary use of _coerce_scalar_to_timedelta_type
In nearly all the places where its used, we can just use `Timedelta` instead.  Way simpler, avoids using a private function.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24793?src=pr&el=h1) Report
> Merging [#24793](https://codecov.io/gh/pandas-dev/pandas/pull/24793?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/17a6bc56e5ab6ad3dab12d3a8b20ed69a5830b6f?src=pr&el=desc) will **decrease** coverage by `49.47%`.
> The diff coverage is `33.33%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24793/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24793?src=pr&el=tree)

```diff
@@             Coverage Diff             @@
##           master   #24793       +/-   ##
===========================================
- Coverage   92.38%   42.91%   -49.48%     
===========================================
  Files         166      166               
  Lines       52382    52379        -3     
===========================================
- Hits        48395    22478    -25917     
- Misses       3987    29901    +25914
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `?` | |
| #single | `42.91% <33.33%> (-0.02%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24793?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/dtypes/cast.py](https://codecov.io/gh/pandas-dev/pandas/pull/24793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2Nhc3QucHk=) | `48.67% <0%> (-40.06%)` | :arrow_down: |
| [pandas/core/indexes/timedeltas.py](https://codecov.io/gh/pandas-dev/pandas/pull/24793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy90aW1lZGVsdGFzLnB5) | `44.41% <0%> (-45.84%)` | :arrow_down: |
| [pandas/core/computation/pytables.py](https://codecov.io/gh/pandas-dev/pandas/pull/24793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vcHl0YWJsZXMucHk=) | `92.04% <100%> (-0.33%)` | :arrow_down: |
| [pandas/io/formats/latex.py](https://codecov.io/gh/pandas-dev/pandas/pull/24793/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvbGF0ZXgucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/core/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/24793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY2F0ZWdvcmljYWwucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/sas/sas\_constants.py](https://codecov.io/gh/pandas-dev/pandas/pull/24793/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXNfY29uc3RhbnRzLnB5) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/tseries/plotting.py](https://codecov.io/gh/pandas-dev/pandas/pull/24793/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvcGxvdHRpbmcucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/tseries/converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/24793/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvY29udmVydGVyLnB5) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/formats/html.py](https://codecov.io/gh/pandas-dev/pandas/pull/24793/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvaHRtbC5weQ==) | `0% <0%> (-99.35%)` | :arrow_down: |
| [pandas/core/groupby/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/24793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS9jYXRlZ29yaWNhbC5weQ==) | `0% <0%> (-95.46%)` | :arrow_down: |
| ... and [125 more](https://codecov.io/gh/pandas-dev/pandas/pull/24793/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24793?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/24793?src=pr&el=footer). Last update [17a6bc5...b7b0169](https://codecov.io/gh/pandas-dev/pandas/pull/24793?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24793?src=pr&el=h1) Report
> Merging [#24793](https://codecov.io/gh/pandas-dev/pandas/pull/24793?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/17a6bc56e5ab6ad3dab12d3a8b20ed69a5830b6f?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24793/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24793?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24793      +/-   ##
==========================================
- Coverage   92.38%   92.38%   -0.01%     
==========================================
  Files         166      166              
  Lines       52382    52379       -3     
==========================================
- Hits        48395    48391       -4     
- Misses       3987     3988       +1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.81% <66.66%> (-0.01%)` | :arrow_down: |
| #single | `42.91% <33.33%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24793?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/computation/pytables.py](https://codecov.io/gh/pandas-dev/pandas/pull/24793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vcHl0YWJsZXMucHk=) | `92.35% <100%> (-0.03%)` | :arrow_down: |
| [pandas/core/dtypes/cast.py](https://codecov.io/gh/pandas-dev/pandas/pull/24793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2Nhc3QucHk=) | `88.7% <100%> (-0.02%)` | :arrow_down: |
| [pandas/core/indexes/timedeltas.py](https://codecov.io/gh/pandas-dev/pandas/pull/24793/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy90aW1lZGVsdGFzLnB5) | `90.22% <100%> (-0.03%)` | :arrow_down: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/24793/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `88.04% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24793?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/24793?src=pr&el=footer). Last update [17a6bc5...b7b0169](https://codecov.io/gh/pandas-dev/pandas/pull/24793?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks, there is 1 last use in pytables I think can be removed? There's one use left in tools.timedeltas (same place where it is defined) and a handful of tests.  I'll see if we can remove it altogether