[Package Renames] Document how to apply for popularity transfers

[loic-sharma]

As part of the package renames epic (#7896), we created a feature that lets authors transfer the popularity of packages. This would let authors make the replacement package discoverable in search results even if the renamed package is popular. For example, the package FAKE was replaced by fake-cli, however, FAKE is still the top result for the "fake" search query.

Originally, the plan was to add UI to let authors customize their popularity transfers. Due to concerns that misusing this advanced feature could hurt nuget.org's search results, we've decided to that popularity transfers should be reviewed by the nuget.org team. Customers will apply for popularity transfers using a process similar to our Package Id prefix reservation process.

/cc @chgill-MSFT

[loic-sharma]

Documentation is written and approved but we are blocking until PMs decide:

• Which PM should handle these requests?
• Should PMs create an internal playbook?