Cache the parsed result of the HelpCommand and HelpTelnetHandler

[BurningCN]

What is the purpose of the change

Cache the parsed result of the HelpCommand and HelpTelnetHandler to avoid repeated parsing and processing

[codecov-commenter]

Codecov Report

Merging #7919 (e3a2d04) into master (e845e16) will increase coverage by 1.18%.
The diff coverage is 76.66%.

@@             Coverage Diff              @@
##             master    #7919      +/-   ##
============================================
+ Coverage     59.28%   60.46%   +1.18%     
- Complexity      529      545      +16     
============================================
  Files          1077     1089      +12     
  Lines         43565    43849     +284     
  Branches       6368     6403      +35     
============================================
+ Hits          25826    26514     +688     
+ Misses        14879    14363     -516     
- Partials       2860     2972     +112     

Impacted Files	Coverage Δ
...ting/telnet/support/command/HelpTelnetHandler.java	77.41% <74.07%> (+2.41%)	⬆️
...n/java/org/apache/dubbo/qos/command/impl/Help.java	83.33% <100.00%> (+0.57%)	⬆️
.../dubbo/remoting/transport/MultiMessageHandler.java	80.00% <0.00%> (-20.00%)	⬇️
...bo/rpc/cluster/support/FailbackClusterInvoker.java	52.45% <0.00%> (-18.04%)	⬇️
...in/java/org/apache/dubbo/common/utils/JVMUtil.java	81.13% <0.00%> (-11.33%)	⬇️
...o/remoting/transport/ChannelHandlerDispatcher.java	60.00% <0.00%> (-10.00%)	⬇️
...ting/exchange/support/header/HeartbeatHandler.java	83.72% <0.00%> (-9.31%)	⬇️
...va/org/apache/dubbo/rpc/support/ProtocolUtils.java	61.53% <0.00%> (-8.03%)	⬇️
...bbo/config/bootstrap/builders/ConsumerBuilder.java	93.10% <0.00%> (-6.90%)	⬇️
...apache/dubbo/rpc/cluster/support/ClusterUtils.java	60.00% <0.00%> (-6.04%)	⬇️
... and 133 more

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[AlbumenJ]

Would it be better to change to WeakReference?

[BurningCN]

Would it be better to change to WeakReference?

Thank you for your suggestion. The help command is less important than others. I have modified the map type to WeakHashMap