Add connection num feature

[nanfeng1999]

SOFA-RPC 新手任务 自定义rest协议的用户连接数

[codecov]

Codecov Report

Merging #1038 (ef06533) into master (faa68b0) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##             master    #1038      +/-   ##
============================================
- Coverage     11.39%   11.38%   -0.02%     
  Complexity       41       41              
============================================
  Files           312      312              
  Lines          9193     9207      +14     
  Branches       1266     1270       +4     
============================================
  Hits           1048     1048              
- Misses         7987     8001      +14     
  Partials        158      158              

Impacted Files	Coverage Δ
...t/runtime/adapter/helper/ConsumerConfigHelper.java	0.00% <0.00%> (ø)
...c/boot/runtime/binding/RpcBindingXmlConstants.java	0.00% <ø> (ø)
...pc/boot/runtime/converter/RpcBindingConverter.java	0.00% <0.00%> (ø)
...y/sofa/rpc/boot/runtime/param/RpcBindingParam.java	0.00% <0.00%> (ø)

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[HzjNeverStop]

LGTM