DataFrame.sum() with mix of timedelta and IntegerNA returns NA for IntNA
```python
In [43]: df = pd.DataFrame({"A": pd.to_timedelta([0, 1, None]), "B": pd.array([1, 2, None], dtype='Int32')})

In [44]: df.sum()
Out[44]:
A   00:00:00.000000
B               NaT
dtype: timedelta64[ns]
```

cc @jbrockmendel 

Not a blocker for the RC, but is a blocker for the release.