checksum property of `os_images` is not authorized in os_images of s-c-c

According to the os_images schema in sylva-core, an image can be defined via :

os_images:
  foo
    uri: oci://x.x.x.x/sylva/foo
    filename: foo_image.raw
    k8s-flavor: rke2
    checksum: foochecksum

The os_images will then be forwarded to sylva-capi-cluster (https://gitlab.com/sylva-projects/sylva-core/-/blob/main/charts/sylva-units/values.yaml?ref_type=heads#L1725) via the configmap created thanks to create-os-images-info.sh (https://gitlab.com/sylva-projects/sylva-core/-/blob/main/charts/sylva-units/scripts/create-os-images-info.sh?ref_type=heads#L45). All the "user" properties of an os-image are added to the CM https://gitlab.com/sylva-projects/sylva-core/-/blob/main/charts/sylva-units/scripts/create-os-images-info.sh?ref_type=heads#L40

But It seems that the checksum property is not authorized in the sylva-capi-cluster os_images schema (https://gitlab.com/sylva-projects/sylva-elements/helm-charts/sylva-capi-cluster/-/blob/main/values.schema.yaml?ref_type=heads#L1496) (which is authorised in the sylva-core schema https://gitlab.com/sylva-projects/sylva-core/-/blob/main/charts/sylva-units/values.schema.yaml?ref_type=heads#L791). The Checksum property should perhaps be replaced by md5 and sha256 ?

cc @cristian.manda