[BUG] make_feature_column_workflow doesn't work with categorical columns

[benfred]

Since the API overhaul in 0.4 - the make_feature_column_workflow function doesn't work with categorical data.

The problem is that its trying to directly set the category statistics on the workflow https://github.com/NVIDIA/NVTabular/blob/8b834310680154c102237b14cd36c165aa5c4cff/nvtabular/framework_utils/tensorflow/feature_column_utils.py#L292-L301

We should update to using a fit categorify op - and add a test to catch this in the future