Use documented repo structure for apps in Flux2

[schnatterer]

For Fluxv2 change to recommended repo structure, described here.

That is, apps should be deployed to apps/<stage> instead of clusters/<stage>

Our repo currently looks like this

fluxv2
└── clusters
    └── gitops-playground
        ├── flux-system
        │   ├── gotk-components.yaml
        │   ├── gotk-sync.yaml
        │   └── kustomization.yaml
        ├── fluxv2-production
        │   └── spring-petclinic-plain
        │       ├── cm.yaml
        │       ├── deployment.yaml
        │       └── service.yaml
        └── fluxv2-staging
            └── spring-petclinic-plain
                ├── cm.yaml
                ├── deployment.yaml
                └── service.yaml

whereas this is recommended:

├── apps
│   ├── production 
│   └── staging
└── clusters
    ├── production
    └── staging

[CloudoguSiebels]

We are removing Flux from the playground.