Add inplace support for rename_axis
 - [x] closes #15704 
 - [x] tests added / passed
 - [x] passes ``git diff upstream/master --name-only -- '*.py' | flake8 --diff``
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16505?src=pr&el=h1) Report
> Merging [#16505](https://codecov.io/gh/pandas-dev/pandas/pull/16505?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/e81f3cc30725443a1d36ec27279f3fec4eed60ec?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/16505/graphs/tree.svg?token=eZ4WkYLtcO&src=pr&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/16505?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16505      +/-   ##
==========================================
+ Coverage   90.43%   90.43%   +<.01%     
==========================================
  Files         161      161              
  Lines       51045    51047       +2     
==========================================
+ Hits        46161    46163       +2     
  Misses       4884     4884
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.27% <100%> (ø)` | :arrow_up: |
| #single | `40.16% <16.66%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16505?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/16505?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `92.17% <100%> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16505?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/16505?src=pr&el=footer). Last update [e81f3cc...7011067](https://codecov.io/gh/pandas-dev/pandas/pull/16505?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/16505?src=pr&el=h1) Report
> Merging [#16505](https://codecov.io/gh/pandas-dev/pandas/pull/16505?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/344cec77f1904343f8d253d7cfd8d5fccddb08de?src=pr&el=desc) will **decrease** coverage by `0.02%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16505/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/16505?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16505      +/-   ##
==========================================
- Coverage   90.95%   90.92%   -0.03%     
==========================================
  Files         161      161              
  Lines       49276    49278       +2     
==========================================
- Hits        44817    44807      -10     
- Misses       4459     4471      +12
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.68% <100%> (-0.03%)` | :arrow_down: |
| #single | `40.18% <16.66%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16505?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/16505?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `92.27% <100%> (ø)` | :arrow_up: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/16505?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `63.23% <0%> (-1.82%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16505?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/16505?src=pr&el=footer). Last update [344cec7...01eaba1](https://codecov.io/gh/pandas-dev/pandas/pull/16505?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks @HndrkMkt 