BUG: ExtensionIndex.map doesn't handle na_action correctly
(From `master`)

```python
import pandas as pd

idx = pd.to_datetime(["2020-01-01", None])
idx.map(lambda x: pd.Timestamp("1999-01-01"), na_action="ignore")
# DatetimeIndex(['1999-01-01', '1999-01-01'], dtype='datetime64[ns]', freq=None)

idx = pd.CategoricalIndex(["a", None], categories=["a"])
idx.map(lambda x: x, na_action="ignore")
# TypeError: map() got an unexpected keyword argument 'na_action'
```

In the `DatetimeIndex` case `idx.map` should propagate the null value instead of returning `Timestamp("1999-01-01")` since `na_action == "ignore"`, and although it isn't documented I think `CategoricalIndex.map` should allow `na_action` since the other `map` methods do.