weekly releases needed

currently ubuntu-core-initrd vendors in lots of binaries at build time.

to ensure they are up to date we should trigger rebuilds of ubuntu-core-initrd, or have regular schedule when they release.

also given the success of automatic builds & releases of mantic branch, we should consider enabling automatic releases upon merged to focal & jammy branches too.

and probably have github action to automatically generate weekly commits and thus core-initrd releases.

No files or tests are named. Start by reviewing the existing automatic build and release setup for the mantic branch, then compare the focal and jammy workflows. Define the scheduling, rebuild, and release behavior before deciding what completion should cover.

Written by the indexing model from the issue text.