text: Title: PSI added to diff of numerical stat columns
  Body: **Is your feature request related to a problem? Please describe.**
  Within https://github.com/capitalone/DataProfiler/blob/main/dataprofiler/profilers/numerical_column_stats.py#L350
  Need to add PSI - https://medium.com/model-monitoring-psi/population-stability-index-psi-ab133b0a5d42
  Should be a helper function to calculate which is called withtin the `def diff` function.
  
  
  **Describe the outcome you'd like:**
  receiving PSI in the `diff` command of NumericalStatsMixin
  Tests around the addition.
  
  
  **Additional context:**
  