[SPARK-23268][SQL] Reorganize packages in data source V2
## What changes were proposed in this pull request?
1. create a new package for partitioning/distribution related classes.
As Spark will add new concrete implementations of `Distribution` in new
releases, it is good to
have a new pa
[SPARK-23268][SQL] Reorganize packages in data source V2
## What changes were proposed in this pull request?
1. create a new package for partitioning/distribution related classes.
As Spark will add new concrete implementations of `Distribution` in new
releases, it is good to
have a new pa
