Support Validating Webhook Configuration resource in K8s package

[Vandit1604]

fixes: #718

We aren't supporting ValidatingWebhookConfiguration but using it in our cluster-infra manifest files for prombench.

[Vandit1604]

I guess circleci failed because of my committed go.mod and go.sum. Removed them from the PR to check if that's the case.

[yomek33]

I've encountered an error while applying a ValidatingWebhookConfiguration:

13:07:44 k8s.go:545: resource created - kind: Job, name: ingress-nginx-admission-patch
13:07:54 provider.go:74: Request for 'running job:ingress-nginx-admission-patch' is done!
13:07:54 k8s.go:703: resource updated - kind: IngressClass, name: nginx
Error parsing commandline arguments: error applying 'manifests/cluster-infra/2_ingress-nginx-controller.yaml' err:resource update failed - kind: ValidatingWebhookConfiguration, name: ingress-nginx-admission: validatingwebhookconfigurations.admissionregistration.k8s.io "ingress-nginx-admission" is invalid: metadata.resourceVersion: Invalid value: 0x0: must be specified for an update
usage: infra kind resource apply

It seems related to missing resourceVersion during an update.

[yomek33]

I think adding the following code can resolve the issue

if req.ResourceVersion == "" {
	req.ResourceVersion = l.ResourceVersion
}

[Vandit1604]

Thanks @yomek33 for pointing this out.

[Vandit1604]

Updated with changes. Thanks @yomek33

[jesusvazquez]

LGTM very related to your previous change in #716