[Enhancement] Support sidecars

[yandongxiao]

Related Issue(s)

Fixes: #411

For example, we can add a sidecar on FE/BE/CN Component.

    sidecars:
    - name: hello-world-container
      image: busybox
      command: ['sh', '-c', 'echo "Hello World From CN" && sleep 3600']
      resources:
        requests:
          memory: "6Mi"
          cpu: "25m"
        limits:
          memory: "128Mi"
          cpu: "500m"

The result is:

➜  k get pods
NAME                                       READY   STATUS    RESTARTS   AGE
kube-starrocks-be-0                        2/2     Running   0          2m1s
kube-starrocks-cn-0                        2/2     Running   0          41s
kube-starrocks-fe-0                        2/2     Running   0          2m33s
kube-starrocks-operator-6544bf4f89-gst6r   1/1     Running   0          3m2s
➜  k logs kube-starrocks-fe-0  -c hello-world-container
Hello World From FE
➜  k logs kube-starrocks-be-0  -c hello-world-container
Hello World From BE
➜  k logs kube-starrocks-cn-0  -c hello-world-container
Hello World From CN