support referencing cluster authentication info from secrets

[Iceber]

What type of PR is this?

/kind feature

What this PR does / why we need it:
Clusterpedia will only fetch secrets from the specified namespace, which is set by the --namespace flag, indicating the namespace where Clusterpedia is running.

apiVersion: cluster.clusterpedia.io/v1alpha2
kind: PediaCluster
metadata:
  name: cluster-example
spec:
  apiserver: "https://cluster-example.io:8080"
  authenticationFrom:
    kubeconfig:
      name: "cluster-example-auth"
      key: "kubeconfig"
    ca:
      name: "cluster-example-auth"
      key: "ca.crt"
    cert:
      name: "cluster-example-auth"
      key: "client.crt"
    key:
      name: "cluster-example-auth"
      key: "client.key"
    token:
      name: "cluster-example-auth"
      key: "token"

Which issue(s) this PR fixes:
issue: #680

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[clusterpedia-bot]

Hi @Iceber,
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