Add ClusterTransport and ClusterToken interface so that cluster client and cluster server can has the same action

[all4you]

Describe what this PR does / why we need it

• Extract a super interface com.alibaba.csp.sentinel.cluster.ClusterToken for:

  • {@link com.alibaba.csp.sentinel.cluster.client.ClusterTokenClient}
  • {@link com.alibaba.csp.sentinel.cluster.server.ClusterTokenServer}

• Extract a super interface com.alibaba.csp.sentinel.cluster.ClusterTransport for:

  • {@link com.alibaba.csp.sentinel.cluster.ClusterTransportClient}
  • {@link com.alibaba.csp.sentinel.cluster.ClusterTransportServer}

• NettyTransportServer should not implements the ClusterTokenServer because it is a TransportServer not a TokenServer.
  So it should implements a TransportServer which maybe like ClusterTransportServer
  just like the NettyTransportClient implements ClusterTransportClient

Does this pull request fix one issue?

• Unified the ClusterTransportClient and ClusterTransportServer with a same super interface ClusterTransport
• Unified the ClusterTokenClient and ClusterTokenServer with a same super interface ClusterToken

[codecov-io]

Codecov Report

Merging #444 into master will decrease coverage by 0.2%.
The diff coverage is 51%.

@@             Coverage Diff              @@
##             master     #444      +/-   ##
============================================
- Coverage     37.77%   37.57%   -0.21%     
- Complexity      984     1104     +120     
============================================
  Files           235      259      +24     
  Lines          7409     8213     +804     
  Branches       1016     1120     +104     
============================================
+ Hits           2799     3086     +287     
- Misses         4251     4732     +481     
- Partials        359      395      +36

Impacted Files	Coverage Δ	Complexity Δ
...mmand/handler/FetchClusterClientConfigHandler.java	0% <ø> (ø)	0 <0> (?)
.../handler/ModifyClusterServerFlowConfigHandler.java	0% <ø> (ø)	0 <0> (ø)	⬇️
...mand/handler/ModifyClusterClientConfigHandler.java	0% <ø> (ø)	0 <0> (?)
...mmand/handler/GetParamFlowRulesCommandHandler.java	0% <ø> (ø)	0 <0> (ø)	⬇️
...d/handler/FetchClusterFlowRulesCommandHandler.java	0% <ø> (ø)	0 <0> (ø)	⬇️
.../command/handler/FetchTopParamsCommandHandler.java	0% <ø> (ø)	0 <0> (ø)	⬇️
...sentinel/slots/block/flow/param/ParamFlowRule.java	53.7% <ø> (+1.85%)	18 <0> (+1)	⬆️
.../handler/ModifyClusterFlowRulesCommandHandler.java	0% <ø> (ø)	0 <0> (ø)	⬇️
...mmand/handler/FetchClusterServerConfigHandler.java	0% <ø> (ø)	0 <0> (ø)	⬇️
...dler/FetchClusterParamFlowRulesCommandHandler.java	0% <ø> (ø)	0 <0> (ø)	⬇️
... and 94 more

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