[feature request]Refactor yurtctl init to call sealer to initialize OpenYurt cluster

[Peeknut]

What would you like to be added:
As mentioned in the issue #656 , after we can use sealer to initialize an OpenYurt cluster, how about refactor yurtctl init to call sealer(https://github.com/alibaba/sealer) to initialize the cluster?

Why is this needed:
1.We can remove the dependency of k8s.io/kubernetes in yurtctl init .(issue #550 )
2.Using yurtctl init to initialize the cluster instead of using sealer can unify the interface of cluster installation and is more user-friendly.

others
/kind feature
/kind good-first-issue