arrstack: mount legacy mediafs CephFS via static PV/PVC

Exposes the legacy mediafs filesystem to the arrstack namespace for the
upcoming mediamover tool. Adds a ceph-mediafs-secret VaultStaticSecret in
csi-cephfs and a 10Ti static RWX PV/PVC pair bound by claimRef.

apps/base/csi-cephfs/kustomization.yaml

@@ -6,5 +6,6 @@ resources:
   - namespace.yaml
   - vaultauth.yaml
   - vaultstaticsecret.yaml
+  - vaultstaticsecret-mediafs.yaml
   - storageclass.yaml
   - vmservicescrape.yaml