Mega Feature: Add kro cli

[candonov]

Feature Description

Problem Statement:
Add a cli for kro and integrate it with kubectl.

Proposed Solution:

The cli should support a diff functionality using --dry-run:

kubectl kro apply -f <updatdRG>.yaml --dry-run
kubectl kro apply -f <updatedInstance>.yaml --dry-run

It should also show the chain dependent resources of an instance and their statuses:

NAME                                  STATE    SYNCED   AGE
webappInstance                        ACTIVE   True     42h
       ├── deployment                 ACTIVE   True     42h
       ├── service                    ACTIVE   True     42h
       └── ingress                    ACTIVE   True     42h

Alternatives Considered:

Additional Context:

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[amirahav]

We believe that the biggest benefits of having the CLI would be around schema validation, linting of the expression language, having an ability of doing a dry-run on the ResourceGroup as well as an ability to produce the complete CRD that would be generated by the ResourceGroup.

In addition, it would be beneficial if there would be a way to view the effects of changes to the ResourceGroup on the instances prior to the ResourceGroup changes being made. eg, there is a proposed change to the ResourceGroup it would be very helpful to know how that change would affect all the instances of that ResourceGroup.