Range fields should accept scalar values when querying

[jarshwah]

93c37c9 assumes that a range should always be passed when querying a range field, but that's not the case, particularly when performing a contains query:

Model.objects.filter(period__contains=datetime.datetime(2024, 3, 1))
# TypeError(FiniteDateTimeRangeField may only accept FiniteDatetimeRange objects)

We're too aggressive with the type checking. Django fields are a lot less strict, allowing ranges, tuples, and scalar values: https://github.com/django/django/blob/944745afe2ec45aed30cef799c250107f1364ca7/django/contrib/postgres/fields/ranges.py#L89-L96

We should just follow along, but perhaps prevent the case of using tuples, because the bounds are not well defined in that case.