Upgrade Kustomize to the latest version

[eak13]

Problem description
In an effort to keep Airship current with the latest updates of its supporting components, upgrade Kustomize to the latest version (currently v4.2.0)

Kustomize information can be found here:

• https://kustomize.io/
• https://github.com/kubernetes-sigs/kustomize/
• https://github.com/kubernetes-sigs/kustomize/releases

Proposed change

• Upgrade Kustomize to v4.2.0
• Validate Kustomize still functional & resolve any breaking changes

[aodinokov]

Here is what we can do:

The main issue with 4.1.3 and further (4.2.0) is that there will be conflicting dependencies.
I elaborated on that some time ago here. here is another PR https://review.opendev.org/c/airship/airshipctl/+/788582 that worked some time ago, but since we were not going in that direction it is in merge conflict now.

That means if we want to update only kustomize - we can update it only till 4.1.2, like it's done here:
https://review.opendev.org/c/airship/airshipctl/+/794269 . This PR is ready to be merged if needed.

if we want to keep up with the latest kustomize (which is a good idea for many reasons :) ), we can proceed in another way:
we need to get rid of ClusterApi dependency first by moving all clusterapi operations to krm-function (see Ruslan's PR: https://review.opendev.org/c/airship/airshipctl/+/793701 - it works already).
Once clusterApi disappears it will be possible to bump dependencies much more easily.

[eak13]

Just to note, for patchset 793701, the corresponding issue is #568. Assuming we proceed that way, once merged & we close #568 then we can proceed with this issue.

[aodinokov]

@ak3216 , right... I've rebased 794269 on top of 793701 (made a separate PR: https://review.opendev.org/c/airship/airshipctl/+/800722 - it's in WIP, but looks like at least airshipctl can be compiled with new dependencies including kustomize)

[aodinokov]

https://review.opendev.org/c/airship/airshipctl/+/800722 is on top of 793701. it's complete and green. need to merge 793701, and rebase it and merge

[aodinokov]

@ak3216 , done in https://review.opendev.org/c/airship/airshipctl/+/800722 . We have kustomize 4.2.0 now. Can be closed.

[aaronsheffield]

Closing based on the above merge.