CLN: remove unneeded inheritance from base object
- [x] xref #25725

Bit of a tedious whopper to review (sorry), but this PR removes all instances of inheriting from the base ``object`` from the code base, as dropping Python2 support means that this particular idiom is no longer needed. 

Additionally, as part of the above, I've removed the check in code_checks.sh that classes must inherit, as that is no longer a requirement after dropping Python2. I don't think a different check is possible to do now, but I can change instead of delete the check if anyone thinks that would make sense.

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26128?src=pr&el=h1) Report
> Merging [#26128](https://codecov.io/gh/pandas-dev/pandas/pull/26128?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/06843a864ffa5d5b0f567eb39911e5cadfdd40b9?src=pr&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `98.64%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26128/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26128?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #26128      +/-   ##
==========================================
- Coverage   91.99%   91.98%   -0.02%     
==========================================
  Files         175      175              
  Lines       52387    52384       -3     
==========================================
- Hits        48192    48184       -8     
- Misses       4195     4200       +5
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.53% <98.64%> (-0.01%)` | :arrow_down: |
| #single | `40.74% <94.59%> (-0.14%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26128?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/groupby/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS9vcHMucHk=) | `94.23% <ø> (ø)` | :arrow_up: |
| [pandas/util/\_depr\_module.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvX2RlcHJfbW9kdWxlLnB5) | `0% <0%> (ø)` | :arrow_up: |
| [pandas/util/\_decorators.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvX2RlY29yYXRvcnMucHk=) | `91.34% <100%> (ø)` | :arrow_up: |
| [pandas/io/packers.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3BhY2tlcnMucHk=) | `88.08% <100%> (ø)` | :arrow_up: |
| [pandas/core/reshape/reshape.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9yZXNoYXBlLnB5) | `99.56% <100%> (ø)` | :arrow_up: |
| [pandas/core/dtypes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2Jhc2UucHk=) | `100% <100%> (ø)` | :arrow_up: |
| [pandas/io/formats/format.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvZm9ybWF0LnB5) | `97.91% <100%> (ø)` | :arrow_up: |
| [pandas/core/algorithms.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYWxnb3JpdGhtcy5weQ==) | `94.78% <100%> (ø)` | :arrow_up: |
| [pandas/core/accessor.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYWNjZXNzb3IucHk=) | `98.79% <100%> (ø)` | :arrow_up: |
| [pandas/io/sas/sas7bdat.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXM3YmRhdC5weQ==) | `91.15% <100%> (ø)` | :arrow_up: |
| ... and [42 more](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26128?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/26128?src=pr&el=footer). Last update [06843a8...0c56f26](https://codecov.io/gh/pandas-dev/pandas/pull/26128?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/26128?src=pr&el=h1) Report
> Merging [#26128](https://codecov.io/gh/pandas-dev/pandas/pull/26128?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/1c0f8cf0546120627f4133896c1cfc510667a82d?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/26128/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26128?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #26128      +/-   ##
==========================================
- Coverage   91.99%   91.98%   -0.01%     
==========================================
  Files         175      175              
  Lines       52385    52382       -3     
==========================================
- Hits        48190    48184       -6     
- Misses       4195     4198       +3
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.54% <100%> (-0.01%)` | :arrow_down: |
| #single | `40.73% <95.45%> (-0.15%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26128?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/groupby/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS9vcHMucHk=) | `94.23% <ø> (ø)` | :arrow_up: |
| [pandas/io/packers.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3BhY2tlcnMucHk=) | `88.08% <100%> (ø)` | :arrow_up: |
| [pandas/core/reshape/reshape.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9yZXNoYXBlLnB5) | `99.56% <100%> (ø)` | :arrow_up: |
| [pandas/core/dtypes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2Jhc2UucHk=) | `100% <100%> (ø)` | :arrow_up: |
| [pandas/io/formats/format.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvZm9ybWF0LnB5) | `97.91% <100%> (ø)` | :arrow_up: |
| [pandas/core/algorithms.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYWxnb3JpdGhtcy5weQ==) | `94.78% <100%> (ø)` | :arrow_up: |
| [pandas/core/reshape/concat.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9jb25jYXQucHk=) | `97.2% <100%> (ø)` | :arrow_up: |
| [pandas/core/accessor.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYWNjZXNzb3IucHk=) | `98.79% <100%> (ø)` | :arrow_up: |
| [pandas/io/sas/sas7bdat.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXM3YmRhdC5weQ==) | `91.15% <100%> (ø)` | :arrow_up: |
| [pandas/io/formats/csvs.py](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvY3N2cy5weQ==) | `98.2% <100%> (ø)` | :arrow_up: |
| ... and [38 more](https://codecov.io/gh/pandas-dev/pandas/pull/26128/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26128?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/26128?src=pr&el=footer). Last update [1c0f8cf...3dc58d6](https://codecov.io/gh/pandas-dev/pandas/pull/26128?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 ```
cripts/validate_docstrings.py(226,): error :  Found unwanted pattern: class Docstring(object)
scripts/tests/test_validate_docstrings.py(13,): error :  Found unwanted pattern: class GoodDocStrings(object)
scripts/tests/test_validate_docstrings.py(256,): error :  Found unwanted pattern: class BadGenericDocStrings(object)
scripts/tests/test_validate_docstrings.py(448,): error :  Found unwanted pattern: class BadSummaries(object)
scripts/tests/test_validate_docstrings.py(487,): error :  Found unwanted pattern: class BadParameters(object)
scripts/tests/test_validate_docstrings.py(614,): error :  Found unwanted pattern: class BadReturns(object)
scripts/tests/test_validate_docstrings.py(697,): error :  Found unwanted pattern: class BadSeeAlso(object)
scripts/tests/test_validate_docstrings.py(735,): error :  Found unwanted pattern: class BadExamples(object)
scripts/tests/test_validate_docstrings.py(773,): error :  Found unwanted pattern: class TestValidator(object)
scripts/tests/test_validate_docstrings.py(954,): error :  Found unwanted pattern: class TestApiItems(object)
``` thanks @topper-123 