[FEA] Internal python _is_homogeneous property

[brandon-b-miller]

Is your feature request related to a problem? Please describe.
It might be useful to have a singular clean and performant way to check if all the columns of a dataframe are of the same dtype, such as a DataFrame property _is_homogeneous. This comes up in a lot of places, such as where we might want to dispatch to a cupy matrix implementation (Transpose, some row wise reductions I believe and some other places), as well as many places we might want to error or warn.

Describe the solution you'd like
A property cudf.DataFrame._is_homogeneous that returns True if all of the datatypes of all of the columns are equal else false. This should be plumbed into the places where we currently use a loop or other means. This might be a good first issue being (hopefully) straightforward and requiring some somewhat broad exploration of the cuDF python layer.

Describe alternatives you've considered
Writing a possibly slightly different loop every time

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

[github-actions]

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[shaneding]

Seems straightforward, if no one is working on this I can take it on :)