Better error for str.cat with listlike of wrong dtype.
- [x] closes #22722
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

This had been blocked on #23167.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26607?src=pr&el=h1) Report
> Merging [#26607](https://codecov.io/gh/pandas-dev/pandas/pull/26607?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/0dbb99efc259c5182ac88f116ebb76ae6e2db6ee?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/26607/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26607?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #26607      +/-   ##
==========================================
- Coverage   91.85%   91.84%   -0.01%     
==========================================
  Files         174      174              
  Lines       50707    50709       +2     
==========================================
- Hits        46578    46576       -2     
- Misses       4129     4133       +4
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.39% <100%> (ø)` | :arrow_up: |
| #single | `41.76% <0%> (-0.09%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26607?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/strings.py](https://codecov.io/gh/pandas-dev/pandas/pull/26607/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc3RyaW5ncy5weQ==) | `98.92% <100%> (ø)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/26607/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `78.94% <0%> (-10.53%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/26607/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97% <0%> (-0.12%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26607?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/26607?src=pr&el=footer). Last update [0dbb99e...81451bd](https://codecov.io/gh/pandas-dev/pandas/pull/26607?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/26607?src=pr&el=h1) Report
> Merging [#26607](https://codecov.io/gh/pandas-dev/pandas/pull/26607?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/a60888ce4ce9e106537fb410688b66baa109edc3?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/26607/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26607?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #26607      +/-   ##
==========================================
- Coverage   91.86%   91.85%   -0.01%     
==========================================
  Files         179      179              
  Lines       50700    50709       +9     
==========================================
+ Hits        46574    46579       +5     
- Misses       4126     4130       +4
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.44% <100%> (ø)` | :arrow_up: |
| #single | `41.09% <21.42%> (-0.1%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26607?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/strings.py](https://codecov.io/gh/pandas-dev/pandas/pull/26607/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc3RyaW5ncy5weQ==) | `98.93% <100%> (+0.01%)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/26607/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `88.88% <0%> (-11.12%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/26607/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.88% <0%> (-0.12%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26607?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/26607?src=pr&el=footer). Last update [a60888c...9752aa7](https://codecov.io/gh/pandas-dev/pandas/pull/26607?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @h-vetinari if you merge master the checks ci failure should be fixed. I think i've seen the Windows py37_np141 failure before. probably a flaky test. likely pass next time around.
 thanks @h-vetinari 