Add `app` label to all `DataPlane` and `ControlPlane` owned resources

[czeslavo]

Problem Statement

Currently, it's not possible to list some of DataPlane and ControlPlane -owned resources with use of the app label because it's not assigned consistently to all of them. Example of a resource that do not have the app label assigned: cluster certificate Secret,

Proposed Solution

Make sure that all of the resources owned by DataPlane and ControlPlane do have the app label assigned with a value equal to the parent's name.

Acceptance Criteria

• [ ] Every object created by DataPlane or ControlPlane controllers have the app label assigned with a value equal to the parent's name
• [ ] As a user, I can use kubectl get <pods|deployments|services|secrets> -l app=<parentName> to list all resources owned by a given DataPlane or ControlPlane

[pmalek]

After checking this it seems that we do this at least for Deployments in https://github.com/Kong/gateway-operator/blob/f6badbef64ac96c78d381f86a48b5b8a60ec4d70/internal/utils/kubernetes/resources/deployments.go#L186 and https://github.com/Kong/gateway-operator/blob/f6badbef64ac96c78d381f86a48b5b8a60ec4d70/internal/utils/kubernetes/resources/deployments.go#L42. We might need to check this for other resources as well though to verify.

[pmalek]

Where we're not using this is for Deployment listing https://github.com/Kong/gateway-operator/blob/f6badbef64ac96c78d381f86a48b5b8a60ec4d70/controllers/dataplane_owned_resources.go#L59-L72, and ingress Service listing https://github.com/Kong/gateway-operator/blob/f6badbef64ac96c78d381f86a48b5b8a60ec4d70/controllers/dataplane_owned_resources.go#L282-L295