many: use bootupd for image.BootcDiskImage

[mvo5]

This commit enables bootupd for the image.BootcDiskImage image type.

[cgwalters]

Note that I still want to do osbuild/bootc-image-builder#18 where bootc owns running bootupd.

[ondrejbudai]

Don't worry, that's still on our plan, this is just an intermediate step: We want to start firstly using the container itself as a buildroot, and then switch fully to bootc.

[achilleas-k]

This commit enables bootupd for the iamge.BootcDiskImage image type.

Typo in the commit message :)

[achilleas-k]

Would you mind breaking this up into multiple commits? Preferably 3 where:

1. Changes in pkg/osbuild/
2. Changes in pkg/manifest/
3. Changes in pkg/image/

There will of course be some changes that need to happen in image when things change in manifest, but that general separation will help with reading the PR (and the history in the future).