[BUG] Endless affinity list when using new schudlingPolicy field

[cjc7373]

Describe the bug
Endless affinity list when using new schudlingPolicy field and a DATA_PLANE_AFFINITY in config

To Reproduce
Steps to reproduce the behavior:

1. Have a DATA_PLANE_AFFINITY: '{"nodeAffinity":{"preferredDuringSchedulingIgnoredDuringExecution":[{"preference":{"matchExpressions":[{"key":"kb-data","operator":"In","values":["true"]}]},"weight":100}]}}' field in the config
2. Create a cluster CR, with schedulingPolicy field not null. e.g.

   spec:
     schedulingPolicy:
       schedulerName: custom-scheduler

3. cluster can't finish reconciling

The cluster CR will become like:

apiVersion: apps.kubeblocks.io/v1alpha1
kind: Cluster
spec:
  ...
  schedulingPolicy:
    affinity:
      nodeAffinity:
        preferredDuringSchedulingIgnoredDuringExecution:
        - preference:
            matchExpressions:
            - key: kb-data
              operator: In
              values:
              - "true"
          weight: 100
        - preference:
            matchExpressions:
            - key: kb-data
              operator: In
              values:
              - "true"
          weight: 100
        - preference:
            matchExpressions:
            - key: kb-data
              operator: In
              values:
              - "true"
          weight: 100
        [repeat hundreds of times]
        ...
    schedulerName: custom-scheduler
    tolerations:
    - effect: NoSchedule
      key: kb-data
      operator: Equal
      value: "true"
    - effect: NoSchedule
      key: kb-data
      operator: Equal
      value: "true"
    - effect: NoSchedule
      key: kb-data
      operator: Equal
      value: "true"
    [repeat hundreds of times]
    ...

Additional context
The root cause is that the generated scheduling policy is patched to cluster CR itself. Though it only should be in the component CR.

On a deeper view, this bug happened because cluster controller would modify cluster CR's spec. In which use case do we need this behavior? After all, the general idea is that a controller will not modify the CR's spec it reconciles.