observability: scrape ceph-csi metrics via VMServiceScrape

The ceph-csi cephfs/rbd charts already expose http-metrics services but
nothing scraped them. Add native VMServiceScrape CRs (the cluster has no
Prometheus-Operator CRDs, only VM-native ones) so the observability
VMAgent (selectAllByDefault) collects ceph-csi grpc/csi metrics.

apps/base/csi-cephrbd/vmservicescrape.yaml

@@ -0,0 +1,15 @@
+---
+# Scrape the ceph-csi-rbd nodeplugin + provisioner http-metrics endpoints.
+# Picked up by the observability VMAgent (selectAllByDefault).
+apiVersion: operator.victoriametrics.com/v1beta1
+kind: VMServiceScrape
+metadata:
+  name: ceph-csi-rbd
+  namespace: csi-cephrbd
+spec:
+  selector:
+    matchLabels:
+      app: ceph-csi-rbd
+  endpoints:
+    - port: http-metrics
+      path: /metrics