Feat: Single cluster deployment application

[yeyeye2333]

What type of PR is this? /kind feature

What this PR does / why we need it: Allow setting the application's destination to a cluster, reducing the operational steps and enabling users to seamlessly use Kurator in a single-cluster, thereby increasing Kurator's flexibility.  Which issue(s) this PR fixes: Fixes #653

Does this PR introduce a user-facing change?: The application can be directly deployed to the current host cluster through the following configuration

apiVersion: apps.kurator.dev/v1alpha1
kind: Application
metadata:
  name: rollout-demo
  namespace: default
spec:
  source:
    gitRepository:
      interval: 3m0s
      ref:
        branch: master
      timeout: 1m0s
      url: https://github.com/stefanprodan/podinfo
  syncPolicies:
    - kustomization:
        interval: 0s
        path: ./deploy/webapp
        prune: true
        timeout: 2m0s
    - kustomization:
        targetNamespace: default
        interval: 5m0s
        path: ./kustomize
        prune: true
        timeout: 2m0s