Move references for kube, image, registry to registry-scanner

[ishitasequeira]

Move references for kube, image, registry to registry-scanner.

Some additional details about breaking out pkg/kube package:
The current pkg/kube in argocd-image-updater references the Application Object which is specific to ArgoCD, I updated the KubernetesClient as below:

type ImageUpdaterKubernetesClient struct {
	ApplicationsClientset versioned.Interface
	KubeClient            *kube.KubernetesClient
}

where, KubernetesClient is as below:

argocd-image-updater/registry-scanner/pkg/kube/kubernetes.go

Lines 16 to 20 in 5ae9a45

	type KubernetesClient struct {
	Clientset kubernetes.Interface
	Context context.Context
	Namespace string
	}

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 75.00000% with 7 lines in your changes missing coverage. Please review.

Project coverage is 63.42%. Comparing base (5ae9a45) to head (6728e9f).

Files with missing lines	Patch %	Lines
cmd/test.go	0.00%	3 Missing ⚠️
pkg/kube/kubernetes.go	40.00%	3 Missing ⚠️
cmd/run.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #998      +/-   ##
==========================================
- Coverage   72.07%   63.42%   -8.66%     
==========================================
  Files          25       15      -10     
  Lines        3653     2212    -1441     
==========================================
- Hits         2633     1403    -1230     
+ Misses        880      723     -157     
+ Partials      140       86      -54     

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[jannfis]

LGTM