Sort added router list before set the 'routers' field of the RouterChain

[tswstarplanet]

What is the purpose of the change

fix a code problem

Brief changelog

Verifying this change

XXXXX

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[codecov-io]

Codecov Report

Merging #3969 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master    #3969      +/-   ##
============================================
+ Coverage     63.99%   63.99%   +<.01%     
  Complexity       98       98              
============================================
  Files           718      718              
  Lines         31609    31609              
  Branches       5088     5088              
============================================
+ Hits          20227    20229       +2     
+ Misses         9062     9060       -2     
  Partials       2320     2320

Impacted Files	Coverage Δ	Complexity Δ
...java/org/apache/dubbo/rpc/cluster/RouterChain.java	96.87% <100%> (ø)	0 <0> (ø)	⬇️
...pache/dubbo/registry/support/AbstractRegistry.java	80.07% <0%> (-2.69%)	0% <0%> (ø)
...dubbo/rpc/protocol/dubbo/CallbackServiceCodec.java	80.14% <0%> (-0.74%)	0% <0%> (ø)
...c/main/java/org/apache/dubbo/rpc/RpcException.java	86.2% <0%> (+3.44%)	0% <0%> (ø)	⬇️
...he/dubbo/remoting/transport/netty/NettyServer.java	73.21% <0%> (+3.57%)	0% <0%> (ø)	⬇️
...apache/dubbo/common/config/ConfigurationUtils.java	72% <0%> (+8%)	0% <0%> (ø)	⬇️
...ache/dubbo/remoting/p2p/support/AbstractGroup.java	56.81% <0%> (+11.36%)	0% <0%> (ø)	⬇️

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[kun-song]

LGTM