Provide a first-class API (as part of App CR status) for discovering deployed resources by App CR

**What steps did you take:**

1. Create a `PackageInstall` via kubectl (not using `kapp deploy`, I mean)
2. Get the generated `App` via kubectl, `kubectl get app my-app -oyaml`

**What happened:**

The `App` does not have any labels/annotations.

**What did you expect:**

I would have expected this App CR to have something like:

```
labels:
kapp.k14s.io/app: "1637859835366892605"
```

**Anything else you would like to add:**

This problem has been discussed at this [Carvel community channel thread](https://kubernetes.slack.com/archives/CH8KCCKA5/p1637842398026700) and there is a temporary workaround: get the ConfigMap whose name is `-ctrl` and get from the Data["spec"] the key `labelValue`.

The motivation main motivation for having this annotation exposed by the App CR is for other clients (like, in my case, the Kubeapps project) to have bidirectional traceability of the resources created as a consequence of an App CR (regardless they're using Kapp or just plain kubectl calls).

Particulary, Kubeapps needs this to display to the users which Kubernetes resources are part of an installation.
Some examples and demo video on the Carvel bundles support in Kubeapps: https://github.com/kubeapps/kubeapps/pull/3816

**Environment:**

- kapp Controller version (execute `kubectl get deployment -n kapp-controller kapp-controller -o yaml` and the annotation is `kbld.k14s.io/images`):
```
- Path: /Users/dhelfand/go/src/github.com/vmware-tanzu/carvel-kapp-controller
Type: local
- Dirty: false
RemoteURL: https://github.com/vmware-tanzu/carvel-kapp-controller
SHA: 8167469ad3d7c61ce1d170e0f809b437308ce070
Tags:
- v0.30.0
```

- Kubernetes version (use `kubectl version`)
```
- Client Version: version.Info{Major:"1", Minor:"22", GitVersion:"v1.22.4", GitCommit:"b695d79d4f967c403a96986f1750a35eb75e75f1", GitTreeState:"clean", BuildDate:"2021-11-17T15:48:33Z", GoVersion:"go1.16.10", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"21", GitVersion:"v1.21.1", GitCommit:"5e58841cce77d4bc13713ad2b91fa0d961e69192", GitTreeState:"clean", BuildDate:"2021-05-21T23:01:33Z", GoVersion:"go1.16.4", Compiler:"gc", Platform:"linux/amd64"}
```

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