SDV 2.0: Remove POC Module

[amontanez24]

Problem Description

As part of the changes for SDV 2.0, we can remove the deprecated POC module and all related code.

Expected behavior

• The functions for simplify_schema and get_random_subset should come directly from sdv.utils.
• Get rid of sdv.utils.poc.

Additional context

• Move the functions in this file to sdv.utils directly