Enhance StringUtils#parseParameters

[GungnirLaevatain]

What is the purpose of the change

precompile regex pattern to avoid compile multiple times

Verifying this change

Pass the org.apache.dubbo.common.utils.StringUtilsTest#testParseParameters

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[codecov-io]

Codecov Report

Merging #5448 into master will decrease coverage by 0.05%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master    #5448      +/-   ##
============================================
- Coverage     61.23%   61.18%   -0.06%     
  Complexity      424      424              
============================================
  Files           919      919              
  Lines         37520    37520              
  Branches       5462     5462              
============================================
- Hits          22975    22956      -19     
- Misses        12036    12053      +17     
- Partials       2509     2511       +2

Impacted Files	Coverage Δ	Complexity Δ
...ava/org/apache/dubbo/common/utils/StringUtils.java	74.92% <100%> (ø)	0 <0> (ø)	⬇️
...rg/apache/dubbo/remoting/utils/PayloadDropper.java	46.15% <0%> (-23.08%)	0% <0%> (ø)
...ache/dubbo/remoting/transport/AbstractChannel.java	75% <0%> (-12.5%)	0% <0%> (ø)
.../remoting/transport/netty4/NettyClientHandler.java	57.62% <0%> (-8.48%)	0% <0%> (ø)
...ng/transport/dispatcher/all/AllChannelHandler.java	62.06% <0%> (-6.9%)	0% <0%> (ø)
.../org/apache/dubbo/remoting/ExecutionException.java	15.78% <0%> (-5.27%)	0% <0%> (ø)
...pache/dubbo/remoting/transport/AbstractServer.java	53.75% <0%> (-3.75%)	0% <0%> (ø)
...c/main/java/org/apache/dubbo/rpc/RpcException.java	80% <0%> (-3.34%)	0% <0%> (ø)
...exchange/support/header/HeaderExchangeHandler.java	61.94% <0%> (-2.66%)	0% <0%> (ø)
...rg/apache/dubbo/common/timer/HashedWheelTimer.java	63.1% <0%> (-0.35%)	0% <0%> (ø)
... and 1 more

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