Update Zookeeper dashboard

[codelipenghui]

We have removed the AspectJ based metrics for ZooKeeper, we need to update the Zookeeper dashboard for Pulsar version which is greater than 2.8

[Bklyn]

There is now a dashboards.template/zookeeper-3.6.json.j2, but it fails to render due to the use of the following variables unknown to Jinja:

• {{instance}}. Should this be $instance?

Traceback (most recent call last):
  File "/tmp/.local/bin/j2", line 8, in <module>
    sys.exit(main())
  File "/tmp/.local/lib/python3.8/site-packages/j2cli/cli.py", line 202, in main
    output = render_command(
  File "/tmp/.local/lib/python3.8/site-packages/j2cli/cli.py", line 186, in render_command
    result = renderer.render(args.template, context)
  File "/tmp/.local/lib/python3.8/site-packages/j2cli/cli.py", line 85, in render
    return self._env \
  File "/tmp/.local/lib/python3.8/site-packages/jinja2/environment.py", line 1291, in render
    self.environment.handle_exception()
  File "/tmp/.local/lib/python3.8/site-packages/jinja2/environment.py", line 925, in handle_exception
    raise rewrite_traceback_stack(source=source)
  File "/tmp/src/apache-pulsar-grafana-dashboard/dashboards.template/zookeeper-3.6.json.j2", line 140, in top-level template code
    "legendFormat": "{{instance}} znode_count",
jinja2.exceptions.UndefinedError: 'instance' is undefined

• {{key}} as in:

  Traceback (most recent call last):
  File "/tmp/.local/bin/j2", line 8, in <module>
  sys.exit(main())
  File "/tmp/.local/lib/python3.8/site-packages/j2cli/cli.py", line 202, in main
  output = render_command(
  File "/tmp/.local/lib/python3.8/site-packages/j2cli/cli.py", line 186, in render_command
  result = renderer.render(args.template, context)
  File "/tmp/.local/lib/python3.8/site-packages/j2cli/cli.py", line 85, in render
  return self._env \
  File "/tmp/.local/lib/python3.8/site-packages/jinja2/environment.py", line 1291, in render
  self.environment.handle_exception()
  File "/tmp/.local/lib/python3.8/site-packages/jinja2/environment.py", line 925, in handle_exception
  raise rewrite_traceback_stack(source=source)
  File "/tmp/src/apache-pulsar-grafana-dashboard/dashboards.template/zookeeper-3.6.json.j2", line 448, in top-level template code
  "legendFormat": "write_per_namespace:{{key}}",