Refactor apply.go to split code into smaller related chunks

[Waterdrips]

apply.go is ca. 800 lines, it does everything, its hard to see what happens where. My IDE can be used to jump about, but logically separating stuff may be better?

We could also potentially refactor arkade to provide a pkg we could import and use here? We do a lot of the same stuff in both (install OpenFaaS, CertManager, Minio) and we could add sealed-secrets to there so the bootstrap tool becomes smaller and simpler to follow?

Any thoughts, comments etc?