Report that shows all packages that have not a single stable version in any arch

[Flowdalic]

Please add a report (per maintainer and maybe even global) that shows all packages that have not a single stable version in any arch.

Such a report is helpful to identify spots where we are missing out on a stable version and also hopefully encourages the maintainer to stabilize their currently unstable only packages. Bonus points if packages only show up if their oldest stabilization candidate has been in ::gentoo for more than 30 days.