feat：add rlock for string func

[Poor12]

String func is also used in a multi-threaded environment, and rlock is required to avoid concurrent map reading and writing.

go func(cluster string) {
        ....
	if pod, ok := event.Object.(*corev1.Pod); ok {
		clusterobject.MakePodUnique(pod, cluster)
		retGrv.Set(cluster, pod.ResourceVersion)
		pod.SetResourceVersion(retGrv.String())
		event.Object = pod
	}

	lock.Lock()
	if !isProxyChClosed {
		proxyCh <- event
	}
	lock.Unlock()
      }
....
}(clusters[i].Name)

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 30.82%. Comparing base (3aa1252) to head (15b64d2).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...g/util/aggregatedlister/global_resource_version.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #354      +/-   ##
==========================================
- Coverage   30.84%   30.82%   -0.02%     
==========================================
  Files         162      162              
  Lines       18823    18825       +2     
==========================================
- Hits         5806     5803       -3     
- Misses      12511    12516       +5     
  Partials      506      506              

Flag	Coverage Δ
unittests	30.82% <0.00%> (-0.02%)	⬇️

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