CLN: move safe_sort from core.algorithms to core.sorting
COMPAT: safe_sort will only coerce list-likes to object, not a numpy string type

xref: https://github.com/pandas-dev/pandas/pull/17003#discussion_r128332208
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=h1) Report
> Merging [#17034](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/8d0c025a4584c0f2d412d060c30fe459dc90b53b?src=pr&el=desc) will **decrease** coverage by `0.04%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17034/graphs/tree.svg?height=150&width=650&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17034      +/-   ##
==========================================
- Coverage   91.02%   90.98%   -0.05%     
==========================================
  Files         161      161              
  Lines       49303    49308       +5     
==========================================
- Hits        44878    44862      -16     
- Misses       4425     4446      +21
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.75% <100%> (-0.03%)` | :arrow_down: |
| #single | `40.19% <60.86%> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9iYXNlLnB5) | `95.92% <100%> (ø)` | :arrow_up: |
| [pandas/core/reshape/merge.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9tZXJnZS5weQ==) | `94.21% <100%> (ø)` | :arrow_up: |
| [pandas/core/algorithms.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYWxnb3JpdGhtcy5weQ==) | `94.09% <100%> (-0.34%)` | :arrow_down: |
| [pandas/core/sorting.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc29ydGluZy5weQ==) | `98.19% <100%> (+0.38%)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `63.23% <0%> (-1.82%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.75% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17034?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/17034?src=pr&el=footer). Last update [8d0c025...1e44c70](https://codecov.io/gh/pandas-dev/pandas/pull/17034?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/17034?src=pr&el=h1) Report
> Merging [#17034](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/8d0c025a4584c0f2d412d060c30fe459dc90b53b?src=pr&el=desc) will **decrease** coverage by `0.04%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17034/graphs/tree.svg?token=eZ4WkYLtcO&src=pr&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17034      +/-   ##
==========================================
- Coverage   91.02%   90.98%   -0.05%     
==========================================
  Files         161      161              
  Lines       49303    49308       +5     
==========================================
- Hits        44878    44862      -16     
- Misses       4425     4446      +21
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.75% <100%> (-0.03%)` | :arrow_down: |
| #single | `40.19% <60.86%> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/algorithms.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYWxnb3JpdGhtcy5weQ==) | `94.09% <100%> (-0.34%)` | :arrow_down: |
| [pandas/core/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9iYXNlLnB5) | `95.92% <100%> (ø)` | :arrow_up: |
| [pandas/core/reshape/merge.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9tZXJnZS5weQ==) | `94.21% <100%> (ø)` | :arrow_up: |
| [pandas/core/sorting.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc29ydGluZy5weQ==) | `98.19% <100%> (+0.38%)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `63.23% <0%> (-1.82%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.75% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17034?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/17034?src=pr&el=footer). Last update [8d0c025...1e44c70](https://codecov.io/gh/pandas-dev/pandas/pull/17034?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/17034?src=pr&el=h1) Report
> Merging [#17034](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/8d0c025a4584c0f2d412d060c30fe459dc90b53b?src=pr&el=desc) will **decrease** coverage by `0.04%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17034/graphs/tree.svg?token=eZ4WkYLtcO&src=pr&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17034      +/-   ##
==========================================
- Coverage   91.02%   90.98%   -0.05%     
==========================================
  Files         161      161              
  Lines       49303    49308       +5     
==========================================
- Hits        44878    44862      -16     
- Misses       4425     4446      +21
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.75% <100%> (-0.03%)` | :arrow_down: |
| #single | `40.19% <60.86%> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/algorithms.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYWxnb3JpdGhtcy5weQ==) | `94.09% <100%> (-0.34%)` | :arrow_down: |
| [pandas/core/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9iYXNlLnB5) | `95.92% <100%> (ø)` | :arrow_up: |
| [pandas/core/reshape/merge.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9tZXJnZS5weQ==) | `94.21% <100%> (ø)` | :arrow_up: |
| [pandas/core/sorting.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc29ydGluZy5weQ==) | `98.19% <100%> (+0.38%)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `63.23% <0%> (-1.82%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.75% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17034?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/17034?src=pr&el=footer). Last update [8d0c025...1e44c70](https://codecov.io/gh/pandas-dev/pandas/pull/17034?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
