Models for Privacy Center configuration

[galvana]

Closes PROD-1787

Description Of Changes

Adding plus_privacy_center_config table to store a minimal version of the Privacy Center config.json. Only a subset of the spec is saved to the database, enough for the Admin UI to generate access and erasure requests.

Code Changes

• [ ] Added new plus_privacy_center_config table
• [ ] PrivacyCenterConfig model and schema
• [ ] Validation tests

Steps to Confirm

• [ ] See https://github.com/ethyca/fidesplus/pull/1354

Pre-Merge Checklist

• [ ] All CI Pipelines Succeeded
• Documentation:
  • [ ] documentation complete, PR opened in fidesdocs
  • [ ] documentation issue created in fidesdocs
• [ ] Issue Requirements are Met
• [ ] Relevant Follow-Up Issues Created
• [ ] Update CHANGELOG.md
• [ ] For API changes, the Postman collection has been updated