Upgrade k8s client API to 1.18+

[josephglanville]

Multiple dependencies will shortly necessitate moving to k8s v1.18+ client libraries. This is a breaking change due to introduction of context on most of the API surface for creating resources and such. Istio is the main current feature that will require this upgrade to happen soon however Contour will need it too in order to update to the v1.5.0 client version.

[ukclivecox]

Hi @josephglanville We already have #1675 and #1678
Is this issue referring to further changes required? If so can you specify them?

[josephglanville]

These may be related but I don't think address the actual k8s client-go upgrade and associated dependencies. All of these deps need to be updated in lockstep as I did for external-dns here kubernetes-sigs/external-dns#1627
This can be a pain and especially because upgrading Istio attempts to upgrade gRPC past 1.27 which is another breaking change.

[ukclivecox]

Ok thanks. Will need to understand how this affects the executor and operator as we would want to support pre 1.18 k8s users given many clients are only on 1.14 at most.

[josephglanville]

If I end up being the one to do it I will validate that anyway because our clusters are on v1.15. My understanding is the client is backwards compatible to all 1.X server/cluster versions however so I don't anticipate any issues.

[ukclivecox]

Might be solved by #2088

[RafalSkolasinski]

In #2088 we initially discussed bumping k8s.io deps to v0.17.8

[ukclivecox]

See https://github.com/kubernetes/enhancements/blob/master/keps/sig-api-machinery/20200123-client-go-ctx.md