[ISSUE #3528] fix: The value of ChannelOption.SO_BACKLOG should not be hard-coded.

[XiaoyiPeng]

Make sure set the target branch to develop

What is the purpose of the change

for issue: #3528

Brief changelog

Make the backlog to be configurable, for compatibility with previous versions, it default value is 1024.

The behavior of the backlog argument on TCP sockets changed with Linux 2.2. Now it specifies the queue length for completely established sockets waiting to be accepted, instead of the number of incomplete connection requests. see: https://man7.org/linux/man-pages/man2/listen.2.html

Verifying this change

This commit has unit tests.

[coveralls]

Coverage increased (+0.08%) to 55.087% when pulling 5b38796 on XiaoyiPeng:so_backlog into 0c85c7b on apache:develop.

[codecov-commenter]

Codecov Report

Merging #3529 (5b38796) into develop (4bb99e6) will decrease coverage by 0.16%.
The diff coverage is 71.42%.

@@              Coverage Diff              @@
##             develop    #3529      +/-   ##
=============================================
- Coverage      48.89%   48.73%   -0.17%     
+ Complexity      4658     4642      -16     
=============================================
  Files            555      555              
  Lines          36724    36730       +6     
  Branches        4839     4839              
=============================================
- Hits           17957    17900      -57     
- Misses         16523    16585      +62     
- Partials        2244     2245       +1     

Impacted Files	Coverage Δ
...che/rocketmq/remoting/netty/NettyServerConfig.java	50.00% <50.00%> (ø)
...e/rocketmq/remoting/netty/NettyRemotingServer.java	60.89% <100.00%> (ø)
...che/rocketmq/remoting/netty/NettySystemConfig.java	95.23% <100.00%> (+0.50%)	⬆️
.../broker/subscription/SubscriptionGroupManager.java	54.11% <0.00%> (-16.48%)	⬇️
...tmq/logappender/log4j2/RocketmqLog4j2Appender.java	35.00% <0.00%> (-10.00%)	⬇️
...in/java/org/apache/rocketmq/test/util/MQAdmin.java	38.88% <0.00%> (-5.56%)	⬇️
...ache/rocketmq/broker/topic/TopicConfigManager.java	54.23% <0.00%> (-4.62%)	⬇️
...ache/rocketmq/store/AllocateMappedFileService.java	39.02% <0.00%> (-2.44%)	⬇️
...he/rocketmq/client/trace/AsyncTraceDispatcher.java	78.21% <0.00%> (-1.49%)	⬇️
...mq/client/impl/consumer/RebalanceLitePullImpl.java	48.52% <0.00%> (-1.48%)	⬇️
... and 11 more

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