Officialise image catalog with extensions

[gbartolini]

Now that support for extensions in image catalogs has been merged, we need to officially adopt the updated catalog.

Currently, we have a temporary catalog named catalog-extensions-<OS>.yaml (e.g. https://github.com/cloudnative-pg/artifacts/blob/main/image-catalogs/catalog-extensions-trixie.yaml). We have a couple of options moving forward:

1. Directly add extensions to the existing minimal catalog and rename the current non-extension version to minimal-legacy.yaml (this would remain suitable for pre-1.29 versions and would be dismissed when 1.28 phases out).

2. Add extensions to a new temporary catalog called minimal-with-extensions, announcing that from version 1.31, this catalog will be renamed to minimal.yaml.

3. Similar to the above, but make the separation permanent. In this case, the name could differ from the current catalog-extensions-<OS>.yaml, and we could evaluate a specific type, such as extensions.

What are your thoughts on these options? Are there any other possible alternatives?

[gbartolini]

With @mnencia we were talking of adding a new folder called extensions in the image-catalogs directory where to put the new catalog with the name minimal, and add a kustomization.yaml file that uses the local minimal file and includes the other catalogs from the parent directory.