ENH: allow NaN value in str.place
```python
>>>pd.Series(['A',pd.NA],dtype='string').str.replace(pd.NA,0)
TypeError: repl must be a string or callable
>>>pd.Series(['A',pd.NA],dtype='string').str.replace(0,pd.NA)
TypeError: repl must be a string or callable
```

Now both `str.replace(pd.NA,0)` and `str.replace(0,pd.NA)` raise.

I think it will be better to allow these replacements since `replace` method can handle this.