[FEATURE] review naming columns Steps: CombineColumns, CombineKeys, ExpandColumns

[davidberenstein1957]

Is your feature request related to a problem? Please describe.
The naming for these operations is a bit fragmented and not always as explicit/intuitive.

Describe the solution you'd like
I propose reviewing the naming and perhaps aligning it with a more familiar naming and API design like the one used in pandas.

• ExpandColumns is nice and explicit, but I think pandas uses explode, so something like ExplodeColumns would perhaps be better.
• CombineKeys uses the Keys in the name, but I think it would be better to go for something like AggregateColumns/ MergeColumns, AppendColumns
• CombineColumns seems to groupby operation and not really a combination. Perhaps something like GroupByColumns might be better.

Open to iterating on the naming.

Describe alternatives you've considered
N.A.
Additional context
N.A.

[plaguss]

Hi! I think that can be useful too.

• I think CombineKeys can be renamed to MergeColumns (this one would be the easiest, it's not released yet), it's more explicit, and it's really what it does.
  For the other two, I'm not sure we should follow the same naming convention as pandas:
• CombineColumns I think it works fine with GroupColumns, not necessarily the GroupBy, the operation groups elements in a dictionary, but doesn't group elements in columns in the same sense of a pandas dataframe or a table.
• ExpandColumns given that is explicit as it is, there's no need to change it.