feat: add kustomization for ClusterImageCatalog manifests

[solidDoWant]

This adds a kustomization file that always includes the latest ClusterImageCatalog manifest for the default distribution.

cdc86b7 added support for multiple Debian releases, and changed the ClusterImageCatalog.yaml from a file to a symlink. This is great if you have the repo cloned, but it broke several install methods, including what's listed in the CNPG docs:

• kubectl apply -f https://raw.githubusercontent.com/cloudnative-pg/postgres-containers/main/Debian/ClusterImageCatalog.yaml (as listed in the docs) fails with error validating data: invalid object to validate [...]

• Inclusion in a kustomization.yaml file i.e.

  ---
  apiVersion: kustomize.config.k8s.io/v1beta1
  kind: Kustomization
  resources:
    - https://raw.githubusercontent.com/cloudnative-pg/postgres-containers/refs/heads/main/Debian/ClusterImageCatalog.yaml

  fails with error: accumulating resources: accumulation err [...] missing Resource metadata': [...]

• Installation via flux CD with a git source fails as flux deletes symlinks for security reasons

This fixes all of the above install methods (and probably others) by adding a kustomization.yaml file. Users can specify this file, or in some cases the Debian directory, to install the correct manifest:

• kubectl apply -k kubectl apply -k https://github.com/cloudnative-pg/postgres-containers//Debian/?ref=main

• Inclusion in a kustomization.yaml file i.e.

  ---
  apiVersion: kustomize.config.k8s.io/v1beta1
  kind: Kustomization
  resources:
    - https://github.com/cloudnative-pg/postgres-containers//Debian/?ref=main

• Flux CD git source and Kustomization with path: /Debian

The file will be automatically when the CD pipeline is ran, just like the symlinked ClusterImageCatalog.yaml.

[Joker9944]

Wanted to do the exact same thing. Good stuff.