BUG: rolling does not accept MultiIndex name
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- [ ] (optional) I have confirmed this bug exists on the master branch of pandas.

---

#### Code Sample, a copy-pastable example

If
```python
df = pandas.DataFrame()
df['date'] = pandas.date_range('2021-1-1', '2021-1-5', freq='h')
df.loc[df.date <= '2021-1-3', 'category'] = 'A'
df.loc[df.date > '2021-1-3', 'category'] = 'B'
df.set_index(['category','date'], inplace=True)
df['value'] = 1
```
then
```python
df.groupby('category').rolling('D', on='date')
```
breaks with
```python
ValueError: invalid on specified as date, must be a column (of DataFrame), an Index or None
```

#### Problem description

The [documentation](https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.rolling.html?highlight=rolling#pandas.DataFrame.rolling) states that the `on` argument can be a `MultiIndex` level (and then confusingly adds "rather than the DataFrame's index").

#### Expected Output

`rolling` should accept a `MultiIndex` level. Interestingly,
```python
df.groupby('category').resample('D', level='date')
```
works, but it would be nice to unify the interfaces: `resample` accepts `level` and `on` for index and column respectively, while `rolling` accepts `on` for both.