Ftr : nacos config

[zouyx]

What this PR does:

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (develop@3fd3cf8). Click here to learn what that means.
The diff coverage is 72.11%.

@@            Coverage Diff             @@
##             develop     #357   +/-   ##
==========================================
  Coverage           ?   66.74%           
==========================================
  Files              ?      150           
  Lines              ?     7935           
  Branches           ?        0           
==========================================
  Hits               ?     5296           
  Misses             ?     2137           
  Partials           ?      502

Impacted Files	Coverage Δ
config_center/configurator/mock.go	0% <ø> (ø)
config_center/nacos/factory.go	12.5% <ø> (ø)
remoting/etcdv3/listener.go	46.08% <ø> (ø)
common/extension/config_center.go	0% <ø> (ø)
cluster/directory/static_directory.go	90.47% <ø> (ø)
protocol/protocolwrapper/mock_protocol_filter.go	0% <ø> (ø)
cluster/cluster_impl/failfast_cluster.go	100% <ø> (ø)
cluster/loadbalance/random.go	100% <ø> (ø)
cluster/cluster_impl/registry_aware_cluster.go	100% <ø> (ø)
protocol/jsonrpc/json.go	52.94% <ø> (ø)
... and 136 more

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[AlexStocks]

zouyx, u'd better add some remark for those open funcs.

[zouyx]

i will fix it today , fixed test case yesterday

[flycash]

LGTM

[AlexStocks]

LGTM

[fangyincheng]

LGTM