feat(ci): add CRD schema generation for kubeconform validation

Add scripts to extract OpenAPI v3 schemas from CRD definitions in all
kustomize overlays and write JSON schema files to ci/crd-schemas/ for
kubeconform validation. This allows kubeconform to validate CRD instances
(Elasticsearch, Kibana, CNPG Cluster, VictoriaMetrics, etc.) instead of
skipping or erroring on them.

- ci/generate-crd-schemas.py: extracts schemas from CRD YAML on stdin
- ci/generate-crd-schemas.sh: iterates overlays, pipes to Python script
- ci/validate-apps.sh, ci/validate-clusters.sh: add local schema-location fallback
- Makefile: add generate-schemas target
- add generate-schemas step to kubeconform woodpecker pipeline so schemas

ci/validate-clusters.sh

@@ -6,6 +6,7 @@ KUBE_VERSION="1.33.7"
 schema_args=(
   -schema-location "https://raw.githubusercontent.com/yannh/kubernetes-json-schema/master/{{.NormalizedKubernetesVersion}}-standalone{{.StrictSuffix}}/{{.ResourceKind}}{{.KindSuffix}}.json"
   -schema-location "https://raw.githubusercontent.com/datreeio/CRDs-catalog/main/{{.Group}}/{{.ResourceKind}}_{{.ResourceAPIVersion}}.json"
+  -schema-location "file://${PWD}/ci/crd-schemas/{{.Group}}/{{.ResourceKind}}_{{.ResourceAPIVersion}}.json"
 )
 
 while IFS= read -r -d "" k; do