grpc connection添加keep-alive

[jianliu]

#589 grpc 连接增加keepalive，解决极端情况下连接失效无法感知的问题

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 20.58%. Comparing base (1ca6a8b) to head (d1659c1).
Report is 11 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #590      +/-   ##
============================================
+ Coverage     20.46%   20.58%   +0.12%     
- Complexity      833      840       +7     
============================================
  Files           334      339       +5     
  Lines         13233    13495     +262     
  Branches       1702     1735      +33     
============================================
+ Hits           2708     2778      +70     
- Misses        10171    10363     +192     
  Partials        354      354              

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