Integrating buildah into sealer to make image module stable

[justadogistaken]

Type: feature request

Issue Description(Motivation)

Currently, sealer build/push/pull image by itself, it makes sealer often fails. And some info of sealer image can't be exhibited in imagehub normally.

Nowdays, we have to refactor the image module based on some mature libraries.for fixing image-relevant issues. And it's urgent to make sealer image structure stable. now that the oci image format specification had been made long time ago, and there are several professional tools of building oci-image, why not just use it?

Describe what feature you want

Core Function From Buildah

func BuildDockerfiles(ctx context.Context, store storage.Store, options define.BuildOptions, paths ...string) (id string, ref reference.Canonical, err error)

There is a core function from buildah, and we can call this function to get an oci-image. But this method support Four instructions only. FROM/RUN/ADD/COPY.
So it's incompatible with [Proposal] A more k8s-based/rootfs-transparent instructions in Kubefile. Then we may need to develop a semantic translator to generate final Kubefile for being compatible with more instructions of sealer.