Add Shopper Insights Demo feature

[scannillo]

JIRA DTBTSDK-3174

Summary of changes

• This PR takes a "path of least resistance" approach and restores the old PreferredPaymentMethods demo feature (see old file)
• I made only the necessary updates to this file to get it renamed to ShopperInsights & updated for BT iOS V6 API changes
  • Note: This ViewController could use some clean-up, but I figured we can 🏈 punt on it, since we're pretty slammed with feature requests right now (and ShopperInsights will fluctuate a lot the coming weeks)

Checklist

• ~Added a changelog entry~

Authors

@scannillo