[FEA]: Preserve RangeIndex in more setops cases

[mroeschke]

Is your feature request related to a problem? Please describe.
Sometimes the result of difference, intersection, union could still be represented as a `RangeIndex

In [3]: from cudf import *

In [4]:         idx = Index(range(4))[::-1]
   ...:         other = Index(range(3, 4))
   ...: 
   ...:         result = idx.difference(other)

In [5]: idx
Out[5]: RangeIndex(start=3, stop=-1, step=-1)

In [6]: other
Out[6]: RangeIndex(start=3, stop=4, step=1)

In [7]: result
Out[7]: Int64Index([0, 1, 2], dtype='int64')

Describe the solution you'd like
In the case above, RangeIndex(0, 3, 1) could have been returned

Describe alternatives you've considered
Casting directly to a RangeIndex

Additional context
Add any other context, code examples, or references to existing implementations about the feature request here.