bug: storageClassName field in Fluentd buffer instance not taken into account

[antrema]

Describe the issue

When creating an instance of Fluentd specifying a storageClassName for the buffer, this information is not taken into account

To Reproduce

Create a Fluentd instance with below manifest

---
apiVersion: fluentd.fluent.io/v1alpha1
kind: Fluentd
metadata:
  labels:
    app.kubernetes.io/name: fluentd
  name: fluentd
  namespace: fluent
spec:
  buffer:
    pvc:
      apiVersion: v1
      kind: PersistentVolumeClaim
      spec:
        accessModes:
        - ReadWriteOnce
        resources:
          requests:
            storage: 1Gi
        storageClassName: sata-0a
  fluentdCfgSelector:
    matchLabels:
      config.fluentd.fluent.io/enabled: "true"
  globalInputs:
  - forward:
      bind: 0.0.0.0
      port: 24224
  image: kubesphere/fluentd:v1.15.3
  replicas: 2
  resources:
    limits:
      cpu: 2000m
      memory: 2000Mi
    requests:
      cpu: 100m
      memory: 128Mi

The generated StatefulSet is as follow
kubectl get sts fluentd -n fluent -o yaml

apiVersion: apps/v1
kind: StatefulSet
metadata:
  labels:
    app.kubernetes.io/component: fluentd
    app.kubernetes.io/instance: fluentd
    app.kubernetes.io/name: fluentd
  name: fluentd
  namespace: fluent
  ownerReferences:
  - apiVersion: fluentd.fluent.io/v1alpha1
    blockOwnerDeletion: true
    controller: true
    kind: Fluentd
    name: fluentd
spec:
  podManagementPolicy: OrderedReady
  replicas: 2
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      app.kubernetes.io/component: fluentd
      app.kubernetes.io/instance: fluentd
      app.kubernetes.io/name: fluentd
  serviceName: ""
  template:
    metadata:
      labels:
        app.kubernetes.io/component: fluentd
        app.kubernetes.io/instance: fluentd
        app.kubernetes.io/name: fluentd
      name: fluentd
      namespace: fluent
    spec:
      containers:
      - env:
        - name: BUFFER_PATH
          value: /buffers
        image: kubesphere/fluentd:v1.15.3
        imagePullPolicy: IfNotPresent
        name: fluentd
        ports:
        - containerPort: 2021
          name: metrics
          protocol: TCP
        - containerPort: 24224
          name: forward
          protocol: TCP
        resources:
          limits:
            cpu: "2"
            memory: 2000Mi
          requests:
            cpu: 100m
            memory: 128Mi
        terminationMessagePath: /dev/termination-log
        terminationMessagePolicy: File
        volumeMounts:
        - mountPath: /fluentd/etc
          name: config
          readOnly: true
        - mountPath: /buffers
          name: fluentd-buffer-pvc
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      schedulerName: default-scheduler
      securityContext: {}
      serviceAccount: fluentd
      serviceAccountName: fluentd
      terminationGracePeriodSeconds: 30
      volumes:
      - name: config
        secret:
          defaultMode: 420
          secretName: fluentd-config
  updateStrategy:
    rollingUpdate:
      partition: 0
    type: RollingUpdate
  volumeClaimTemplates:
  - apiVersion: v1
    kind: PersistentVolumeClaim
    metadata:
      creationTimestamp: null
      labels:
        app.kubernetes.io/component: fluentd
        app.kubernetes.io/instance: fluentd
        app.kubernetes.io/name: fluentd
      name: fluentd-buffer-pvc
      namespace: fluent
    spec:
      accessModes:
      - ReadWriteOnce
      resources:
        requests:
          storage: 1Gi
      volumeMode: Filesystem
    status:
      phase: Pending

The storageClassName specification is missing in generated StatefulSet

Expected behavior

Expecting to have a storageClassName specification in volumeClaimTemplates section

Your Environment

- Fluent Operator version: v2.2.0
- Container Runtime: containerd://1.6.15
- Operating system: Ubuntu 22.04.1 LTS
- Kernel version: 5.15.0-46-generic

How did you install fluent operator?

kubectl create ns fluent
kubectl apply -f https://raw.githubusercontent.com/fluent/fluent-operator/release-2.2/manifests/setup/setup.yaml

Additional context

No response