[BUG] `cudf.testing.assert_*_equal` raises AssertionError for equivalent `DecimalDtype`d objects

**Describe the bug**
```python
In [1]: import cudf

In [2]: ser = cudf.Series([1], dtype=cudf.Decimal128Dtype(1))

In [3]: cudf.testing.assert_series_equal(ser, ser)

AssertionError: ColumnBase are different

values are different (100.0 %)
[left]: {"[Decimal('1')]"}
[right]: {"[Decimal('1')]"}
```

**Expected behavior**
I would expect no `AssertionError`.

It appears there's a testing function, `dtype_can_compare_equal_to_other`, used in column comparisons that over-zealously assumes two objects with `DecimalDtype`s shouldn't be compared to each other.

**Environment overview (please complete the following information)**
- Environment location: Bare-metal
- Method of cuDF install: from source