API: Revert breaking `.values` changes
User-facing change: `Series[period].values` nad `Series[interval].values`
continues to be an ndarray of objects. Recommend ``.array`` instead.

There are a handful of related places in pandas where we assumed that
``Series[EA].values`` was an EA.

Part of #23995
Hello @TomAugspurger! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/core/base.py`](https://github.com/TomAugspurger/pandas/blob/39710e4b68f1ba91bd64e8cb7edc6dfcd14b5095/pandas/core/base.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/datetimes.py`](https://github.com/TomAugspurger/pandas/blob/39710e4b68f1ba91bd64e8cb7edc6dfcd14b5095/pandas/core/indexes/datetimes.py) !

 - There are no PEP8 issues in the file [`pandas/core/internals/blocks.py`](https://github.com/TomAugspurger/pandas/blob/39710e4b68f1ba91bd64e8cb7edc6dfcd14b5095/pandas/core/internals/blocks.py) !

 - There are no PEP8 issues in the file [`pandas/core/internals/managers.py`](https://github.com/TomAugspurger/pandas/blob/39710e4b68f1ba91bd64e8cb7edc6dfcd14b5095/pandas/core/internals/managers.py) !

 - There are no PEP8 issues in the file [`pandas/core/reshape/reshape.py`](https://github.com/TomAugspurger/pandas/blob/39710e4b68f1ba91bd64e8cb7edc6dfcd14b5095/pandas/core/reshape/reshape.py) !

 - There are no PEP8 issues in the file [`pandas/tests/extension/base/reshaping.py`](https://github.com/TomAugspurger/pandas/blob/39710e4b68f1ba91bd64e8cb7edc6dfcd14b5095/pandas/tests/extension/base/reshaping.py) !

 - There are no PEP8 issues in the file [`pandas/util/testing.py`](https://github.com/TomAugspurger/pandas/blob/39710e4b68f1ba91bd64e8cb7edc6dfcd14b5095/pandas/util/testing.py) !

 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24163?src=pr&el=h1) Report
> Merging [#24163](https://codecov.io/gh/pandas-dev/pandas/pull/24163?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/c91115172ce1e7324ff9422cb38f520496df2573?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/24163/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24163?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24163      +/-   ##
==========================================
+ Coverage    92.2%    92.2%   +<.01%     
==========================================
  Files         162      162              
  Lines       51700    51712      +12     
==========================================
+ Hits        47670    47682      +12     
  Misses       4030     4030
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.6% <100%> (ø)` | :arrow_up: |
| #single | `43.03% <50%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24163?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/24163/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `87.41% <100%> (ø)` | :arrow_up: |
| [pandas/core/internals/managers.py](https://codecov.io/gh/pandas-dev/pandas/pull/24163/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL21hbmFnZXJzLnB5) | `95.93% <100%> (+0.01%)` | :arrow_up: |
| [pandas/core/internals/blocks.py](https://codecov.io/gh/pandas-dev/pandas/pull/24163/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL2Jsb2Nrcy5weQ==) | `93.67% <100%> (+0.02%)` | :arrow_up: |
| [pandas/core/reshape/reshape.py](https://codecov.io/gh/pandas-dev/pandas/pull/24163/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9yZXNoYXBlLnB5) | `99.56% <100%> (ø)` | :arrow_up: |
| [pandas/core/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/24163/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYmFzZS5weQ==) | `97.64% <100%> (ø)` | :arrow_up: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/24163/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `96.34% <100%> (+0.02%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24163?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/24163?src=pr&el=footer). Last update [c911151...7c22e92](https://codecov.io/gh/pandas-dev/pandas/pull/24163?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/24163?src=pr&el=h1) Report
> Merging [#24163](https://codecov.io/gh/pandas-dev/pandas/pull/24163?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/c91115172ce1e7324ff9422cb38f520496df2573?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/24163/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24163?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24163      +/-   ##
==========================================
+ Coverage    92.2%    92.2%   +<.01%     
==========================================
  Files         162      162              
  Lines       51700    51712      +12     
==========================================
+ Hits        47670    47682      +12     
  Misses       4030     4030
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.6% <100%> (ø)` | :arrow_up: |
| #single | `43.03% <50%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24163?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/24163/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `87.41% <100%> (ø)` | :arrow_up: |
| [pandas/core/internals/managers.py](https://codecov.io/gh/pandas-dev/pandas/pull/24163/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL21hbmFnZXJzLnB5) | `95.93% <100%> (+0.01%)` | :arrow_up: |
| [pandas/core/internals/blocks.py](https://codecov.io/gh/pandas-dev/pandas/pull/24163/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL2Jsb2Nrcy5weQ==) | `93.67% <100%> (+0.02%)` | :arrow_up: |
| [pandas/core/reshape/reshape.py](https://codecov.io/gh/pandas-dev/pandas/pull/24163/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9yZXNoYXBlLnB5) | `99.56% <100%> (ø)` | :arrow_up: |
| [pandas/core/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/24163/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYmFzZS5weQ==) | `97.64% <100%> (ø)` | :arrow_up: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/24163/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `96.34% <100%> (+0.02%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24163?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/24163?src=pr&el=footer). Last update [c911151...7c22e92](https://codecov.io/gh/pandas-dev/pandas/pull/24163?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 lgtm  Only failure was the Azure lining, which has since been fixed on master.

@jorisvandenbossche IIRC, you preferred that `Series[period].values` would return an ndarray of objects right? >  you preferred that Series[period].values would return an ndarray of objects right?

That might be :-) In any case, since then we added `array`, so I think the rationale to keep `.values` backward compatible makes sense. Sounds good. Merging.