these are seriously slowing down builds, adding build flakes in CI due to emulation bugs, and we cannot locally test them nor do we have CI.
with very limited user demand, we're removing them.
- switch to pulling images with containerd in the running base, instead of to the host. this breaks offline kubernetes development but the previous approach with docker pull / save / export cannot be used reliably for multi-arch
- fully qualify images to prepull (needed by ctr)
- fix image architecture in upstream built images, some of which are have the wrong metadata
- move architecture support to warning
