Cannot use downward API in `PackageBuild`

**What steps did you take:**

1. `kctrl package init`
1. Update `PackageBuild` to read values from the downward API

```yaml
apiVersion: kctrl.carvel.dev/v1alpha1
kind: PackageBuild
metadata:
creationTimestamp: null
name: downward.example.com
spec:
release:
- resource: {}
template:
spec:
app:
spec:
deploy:
- kapp: {}
template:
- ytt:
paths:
- carvel
valuesFrom:
- downwardAPI:
items:
- kubernetesAPIs: {}
name: k8s_gvs
- kbld: {}
export:
- imgpkgBundle:
useKbldImagesLock: true
includePaths:
- carvel
```

1. Release/build the package

```shell
kctrl package release --version 0.0.0-mamachanko --tag 0.0.0-mamachanko --copy-to build --yes
```

**What happened:**

```
Prerequisites
1. Host is authorized to push images to a registry (can be set up by running
`docker login`)
2. `package init` ran successfully.

The bundle created needs to be pushed to an OCI registry. (format:
) e.g. index.docker.io/k8slt/sample-bundlekbld builds images when necessary and ensures that all image references are
resolved to an immutable reference
Building images and resolving references
panic: Not implemented

goroutine 1 [running]:
github.com/vmware-tanzu/carvel-kapp-controller/cli/pkg/kctrl/local.(*MinCoreClient).Discovery(0xc000865ee0)
github.com/vmware-tanzu/carvel-kapp-controller/cli/pkg/kctrl/local/min_core_client.go:94 +0x25
github.com/vmware-tanzu/carvel-kapp-controller/pkg/componentinfo.(*ComponentInfo).KubernetesAPIs(0x21a48c8?)
github.com/vmware-tanzu/carvel-kapp-controller@v0.46.0/pkg/componentinfo/component_info.go:80 +0x2d
github.com/vmware-tanzu/carvel-kapp-controller/pkg/app.(*App).template.(*App).buildDownwardAPIAdditionalValues.func3()
github.com/vmware-tanzu/carvel-kapp-controller@v0.46.0/pkg/app/app_template.go:96 +0x3f
github.com/vmware-tanzu/carvel-kapp-controller/pkg/template.DownwardAPIValues.AsYAMLs({{0xc000022480, 0x1, 0x1}, {{{0x0, 0x0}, {0x0, 0x0}}, {{0x271800b, 0xd}, {0x2713bbf, ...}, ...}}, ...})
github.com/vmware-tanzu/carvel-kapp-controller@v0.46.0/pkg/template/downward_api_values.go:74 +0x519
github.com/vmware-tanzu/carvel-kapp-controller/pkg/template.Values.writeFromDownwardAPI({{0xc00032e540, 0x1, 0x1}, {0xc0003788d0, 0xc0003788c0, 0xc0003788e0}, {{0x271800b, 0xd}, {0x2713bbf, 0x9}, ...}, ...}, ...)
github.com/vmware-tanzu/carvel-kapp-controller@v0.46.0/pkg/template/values.go:117 +0x58
github.com/vmware-tanzu/carvel-kapp-controller/pkg/template.Values.AsPaths({{0xc00032e540, 0x1, 0x1}, {0xc0003788d0, 0xc0003788c0, 0xc0003788e0}, {{0x271800b, 0xd}, {0x2713bbf, 0x9}, ...}, ...}, ...)
github.com/vmware-tanzu/carvel-kapp-controller@v0.46.0/pkg/template/values.go:74 +0x51b
github.com/vmware-tanzu/carvel-kapp-controller/pkg/template.(*Ytt).template(0xc000395080, {0xc00030e070, 0x62}, {0x0?, 0x0})
github.com/vmware-tanzu/carvel-kapp-controller@v0.46.0/pkg/template/ytt.go:66 +0x588
github.com/vmware-tanzu/carvel-kapp-controller/pkg/template.(*Ytt).TemplateDir(0xc000866a60?, {0xc00030e070?, 0xc0000061a0?})
github.com/vmware-tanzu/carvel-kapp-controller@v0.46.0/pkg/template/ytt.go:38 +0x45
github.com/vmware-tanzu/carvel-kapp-controller/pkg/app.(*App).template(0xc00017e000, {0xc00030e070, 0x62})
github.com/vmware-tanzu/carvel-kapp-controller@v0.46.0/pkg/app/app_template.go:53 +0x139b
github.com/vmware-tanzu/carvel-kapp-controller/pkg/app.(*App).reconcileFetchTemplateDeploy(0xc00017e000)
github.com/vmware-tanzu/carvel-kapp-controller@v0.46.0/pkg/app/app_reconcile.go:142 +0x452
github.com/vmware-tanzu/carvel-kapp-controller/pkg/app.(*App).reconcileDeploy(0xc00017e000)
github.com/vmware-tanzu/carvel-kapp-controller@v0.46.0/pkg/app/app_reconcile.go:93 +0x65
github.com/vmware-tanzu/carvel-kapp-controller/pkg/app.(*App).Reconcile(0xc00017e000, 0x0)
github.com/vmware-tanzu/carvel-kapp-controller@v0.46.0/pkg/app/app_reconcile.go:50 +0x2ea
github.com/vmware-tanzu/carvel-kapp-controller/pkg/app.(*CRDApp).Reconcile(...)
github.com/vmware-tanzu/carvel-kapp-controller@v0.46.0/pkg/app/crd_app.go:121
github.com/vmware-tanzu/carvel-kapp-controller/pkg/app.(*Reconciler).Reconcile(0xc0002e80f0, {0x2996e28, 0x3757680}, {{{0x2713bbf, 0x9}, {0x271800b, 0xd}}})
github.com/vmware-tanzu/carvel-kapp-controller@v0.46.0/pkg/app/reconciler.go:99 +0x3f4
github.com/vmware-tanzu/carvel-kapp-controller/cli/pkg/kctrl/local.(*Reconciler).Reconcile(0xc000868fd0, {{0xc000818200, 0x1, 0x1}, {0x0, 0x0, 0x0}, {0x0, 0x0, 0x0}, ...}, ...)
github.com/vmware-tanzu/carvel-kapp-controller/cli/pkg/kctrl/local/reconciler.go:144 +0x7e5
github.com/vmware-tanzu/carvel-kapp-controller/cli/pkg/kctrl/cmd/app/release.(*AppSpecBuilder).Build(0xc000869908)
github.com/vmware-tanzu/carvel-kapp-controller/cli/pkg/kctrl/cmd/app/release/app_spec_builder.go:102 +0x879
github.com/vmware-tanzu/carvel-kapp-controller/cli/pkg/kctrl/cmd/package/release.(*ReleaseOptions).Run(0xc0001a5400)
github.com/vmware-tanzu/carvel-kapp-controller/cli/pkg/kctrl/cmd/package/release/release.go:127 +0x505
github.com/vmware-tanzu/carvel-kapp-controller/cli/pkg/kctrl/cmd/package/release.NewReleaseCmd.func1(0xc000593230?, {0x27141d1?, 0xa?, 0x24cd920?})
github.com/vmware-tanzu/carvel-kapp-controller/cli/pkg/kctrl/cmd/package/release/release.go:54 +0x17
github.com/vmware-tanzu/carvel-kapp-controller/cli/pkg/kctrl/cmd.configureGlobalFlags.func1.1(0xc000213be8?, {0xc0001ea150, 0x0, 0x7})
github.com/vmware-tanzu/carvel-kapp-controller/cli/pkg/kctrl/cmd/kctrl.go:141 +0xc3
github.com/cppforlife/cobrautil.DisallowExtraArgs.WrapRunEForCmd.func2.1(0xc000213c90?, {0xc0001ea150, 0x0, 0x7})
github.com/cppforlife/cobrautil@v0.0.0-20221130162803-acdfead391ef/misc.go:45 +0x62
github.com/vmware-tanzu/carvel-kapp-controller/cli/pkg/kctrl/cmd.configureGlobalFlags.WrapRunEForCmd.func3.1(0x11c4d3b?, {0xc0001ea150, 0x0, 0x7})
github.com/cppforlife/cobrautil@v0.0.0-20221130162803-acdfead391ef/misc.go:45 +0x62
github.com/vmware-tanzu/carvel-kapp-controller/cli/pkg/kctrl/cmd.configureGlobalFlags.WrapRunEForCmd.func6.1(0x7?, {0xc0001ea150, 0x0, 0x7})
github.com/cppforlife/cobrautil@v0.0.0-20221130162803-acdfead391ef/misc.go:45 +0x62
github.com/vmware-tanzu/carvel-kapp-controller/cli/pkg/kctrl/cmd.configureTTY.func1.WrapRunEForCmd.func2.1(0xc0000c9c00?, {0xc0001ea150, 0x0, 0x7})
github.com/cppforlife/cobrautil@v0.0.0-20221130162803-acdfead391ef/misc.go:45 +0x62
github.com/spf13/cobra.(*Command).execute(0xc00083adc0, {0xc0001ea0e0, 0x7, 0x7})
github.com/spf13/cobra@v1.6.1/command.go:850 +0x694
github.com/spf13/cobra.(*Command).ExecuteC(0xc000232b00)
github.com/spf13/cobra@v1.6.1/command.go:958 +0x389
github.com/spf13/cobra.(*Command).Execute(0xc0000fea40?)
github.com/spf13/cobra@v1.6.1/command.go:895 +0x13
main.nonExitingMain()
github.com/vmware-tanzu/carvel-kapp-controller/cli/cmd/kctrl/kctrl.go:39 +0x145
main.main()
github.com/vmware-tanzu/carvel-kapp-controller/cli/cmd/kctrl/kctrl.go:21 +0x13
```

It appears as if it wants to read the downward API values from an actual cluster using the discovery client.

**What did you expect:**

That it just builds the package.

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

no

**Environment:**

```
❯ kctrl --version
kctrl version 0.50.2

Succeeded
```

---
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We are also happy to receive and review Pull Requests if you want to help working on this issue.

Start with cli/pkg/kctrl/local/min_core_client.go, especially MinCoreClient.Discovery, then trace how pkg/componentinfo and pkg/template/downward_api_values.go are used during the local package release flow. Reproduce the kctrl package release command and inspect the related app/template paths. Done means PackageBuild downward API values no longer panic during local package construction and the release completes.

Written by the indexing model from the issue text.