Add bindings for `LogicalPlan::Distinct`

[jdye64]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
The Python bindings for DataFusion LogicalPlan::Distinct are missing and should be added to expose that to Python users.

Describe the solution you'd like
Add the file distinct.rs to the Python expr module so that the DataFusion LogicalPlan::Distinct logic can be exposed to and used by Python users.

Describe alternatives you've considered
None

Additional context
None