Merge rancher-backup-crd into rancher-backup using Helm's crds/ directory

[gaetanmetzger]

Summary

Currently, deploying the Rancher Backup Operator requires two separate Helm releases installed in strict order:

helm install rancher-backup-crd # must come first
helm install rancher-backup # fails if CRDs are absent
This is caused by validate-install-crd.yaml which uses lookup() at template render time to verify CRD existence. Since lookup() runs during rendering — before any resources are applied — the CRDs must already be in the cluster when helm install rancher-backup is invoked.

Proposed change

Move the CRD manifests from charts/rancher-backup-crd/templates/ into a crds/ directory at the root of the rancher-backup chart:

rancher-backup/
  crds/
    backup.yaml        ← moved from rancher-backup-crd/templates/
    resourceset.yaml
    restore.yaml
  templates/
    validate-install-crd.yaml   ← can be removed (CRDs guaranteed present)

Helm installs resources in crds/ before rendering any templates (Helm docs — Custom Resource Definitions). This means:

CRDs are applied first
Templates are rendered — lookup() finds the CRDs → no error
Remaining resources are applied
The validate-install-crd.yaml pre-check becomes redundant and can be removed.

Impact

Single helm install rancher-backup — no separate CRD release needed
rancher-backup-crd chart can be deprecated
Simplifies GitOps pipelines and CAPI Addons setups where ordering between HelmChartProxy resources is not guaranteed