Overhaul releasing process (#779)

* CI: instead of migrating docker's action braking changes move to buildah

* CI: try docker v2 action

* CI: correct user var

* CI: copypasta

* CI: debug

* CI: weird action

* CI: hates quotes

* CI: hates all quotes

* CI: masterpiece (debug)

* CI: migrate to docker/build-push-action@v2

* CI: very heavy compilation, gotta be selfhosted

* CI: now image cache ruins the build

* CI: tuning the self-hosted build

* CI: pin checkout

* CI: strip dockerfile; use buildah

* dockerfile: qualify the registry

* dockerfile: fogot to remove chef

* dockerfile: nit

* dockerfile: fryin to guess

* CI: fix tags ang images name

* CI: space separated, right

* CI: ad quoted

* CI: masterpiece (truly)

* CI: noninteractive frontend

* CI: thre's no g++

* Bump LAST_UPDATE dates

* Address some small style nitpicks

Co-authored-by: Hernando Castano <[email protected]>