BUG: IntervalIndex.from_arrays with int64 vs uint64 arrays

```python
ser = pd.Series(range(5))
ser2 = ser.astype("uint64")

ii = pd.IntervalIndex.from_arrays(ser.values, ser2.values)

>>> ii.right.dtype
dtype('uint64')
```

We do some casting in _ensure_simple_new_inputs to check we have matching dtypes, but looks like we miss signed-vs-unsigned cases.
