Update documentation for final integration product integration into Big Bang

Existing product-integration.md talks about how to integrate product into Big Bang after it is approved. This will need to be updated for synergy with the new product integration documents created.

1. Rename to product-integration-supported.md
2. Replace steps covered in other docs with references
3. Add reference to BBTOC process for "graduating" a package
4. Update steps for copying files from existing repo into BigBang repo
5. Steps for validating integration is complete

NOTES:

• Use PodInfo as the example app in all instructions. We want someone following the documents from beginning to end able to add podinfo into Big Bang.
• Placeholders for docs will be created in this MR. Format is markdown.