Add pivot & unpivot (melt) to DataFrame

[ion-elgreco]

Is your feature request related to a problem or challenge?

Pivoting and unpivoting is a common use case for data scientists, this is currently missing in the DF api.

Describe the solution you'd like

Add two methods to DataFrame struct:

• pivot
  • possibility to add distinct values in advance (would be optimized into groupby.agg() directly)
  • let DataFusion calculate distinct values automatically
• unpivot

Describe alternatives you've considered

No response

Additional context

No response

[Omega359]

referenced in apache/datafusion-python#875