BUG: Inserting array of same size with Series.loc raises ValueError
closes #37748
closes #37486
closes #38271
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

cc @phofl Also does this solve #38271 @arw2019 
> Also does this solve #38271 

It seems so:

```
In [1]: import numpy as np 
   ...:     ...: import pandas as pd 
   ...:     ...:  
   ...:     ...: ser = pd.Series(1, index=list("abcde"), dtype="object") 
   ...:     ...:  
   ...:     ...: expected = pd.array([0,0,3,0,0]) 
   ...:     ...: ser.loc["a"] = expected 
   ...:     ...: result = ser[0]                                                                                                                                                                                                               

In [2]: ser                                                                                                                                                                                                                                    
Out[2]: 
a    [0, 0, 3, 0, 0]
b                  1
c                  1
d                  1
e                  1
dtype: object
``` cc @phofl and @jbrockmendel if any comments. lgtm otherwise thanks @ma3da 