API: Datetime/TimedeltaArray from to_datetime
Closes https://github.com/pandas-dev/pandas/issues/24656

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24660?src=pr&el=h1) Report
> Merging [#24660](https://codecov.io/gh/pandas-dev/pandas/pull/24660?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/c4994ca56b5d6af35643bd9f20d39b090acbe5ff?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24660/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24660?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24660      +/-   ##
==========================================
+ Coverage   92.37%   92.37%   +<.01%     
==========================================
  Files         166      166              
  Lines       52384    52388       +4     
==========================================
+ Hits        48391    48395       +4     
  Misses       3993     3993
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.8% <100%> (ø)` | :arrow_up: |
| #single | `43.01% <20%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24660?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/arrays/array\_.py](https://codecov.io/gh/pandas-dev/pandas/pull/24660/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2FycmF5Xy5weQ==) | `100% <100%> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24660?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/24660?src=pr&el=footer). Last update [c4994ca...21007f2](https://codecov.io/gh/pandas-dev/pandas/pull/24660?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/24660?src=pr&el=h1) Report
> Merging [#24660](https://codecov.io/gh/pandas-dev/pandas/pull/24660?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/f57bd72310207b36e96604056f01cb77f0640b3b?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24660/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24660?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24660      +/-   ##
==========================================
+ Coverage   92.37%   92.37%   +<.01%     
==========================================
  Files         166      166              
  Lines       52324    52328       +4     
==========================================
+ Hits        48336    48340       +4     
  Misses       3988     3988
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.8% <100%> (ø)` | :arrow_up: |
| #single | `43.06% <20%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24660?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/arrays/array\_.py](https://codecov.io/gh/pandas-dev/pandas/pull/24660/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2FycmF5Xy5weQ==) | `100% <100%> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24660?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/24660?src=pr&el=footer). Last update [f57bd72...351c781](https://codecov.io/gh/pandas-dev/pandas/pull/24660?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 cc @jorisvandenbossche.

Do the docs make sense, or do they just cause more confusion? lgtm merge on green.