replace hard coded values with constants and small refactor

[khanimteyaz]

What is the purpose of the change

Replace existing hard coded values for dubbo-config below classes

dubbo-common/src/main/java/org/apache/dubbo/common/Constants.java
dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/AbstractConfig.java
dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/AbstractInterfaceConfig.java
dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/AbstractMethodConfig.java
dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/AbstractReferenceConfig.java
dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/ConsumerConfig.java
Along with hard coded value replacement have done small refactoring to use java stream and lambda.

Brief changelog

Hard coded value replacement of few dubbo-config java classes and small refactoring.

Verifying this change

I have run all the existing UT and it passed.

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[codecov-io]

Codecov Report

Merging #3101 into master will decrease coverage by 0.02%.
The diff coverage is 85.29%.

@@             Coverage Diff              @@
##             master    #3101      +/-   ##
============================================
- Coverage      63.6%   63.57%   -0.03%     
  Complexity       75       75              
============================================
  Files           653      653              
  Lines         28218    28214       -4     
  Branches       4803     4800       -3     
============================================
- Hits          17947    17936      -11     
- Misses         8002     8012      +10     
+ Partials       2269     2266       -3

Impacted Files	Coverage Δ	Complexity Δ
...c/main/java/org/apache/dubbo/common/Constants.java	92.85% <ø> (ø)	0 <0> (ø)	⬇️
...n/java/org/apache/dubbo/config/ConsumerConfig.java	92.3% <0%> (ø)	0 <0> (ø)	⬇️
...g/apache/dubbo/config/AbstractReferenceConfig.java	93.75% <100%> (ø)	0 <0> (ø)	⬇️
...n/java/org/apache/dubbo/config/AbstractConfig.java	79.09% <100%> (+0.64%)	0 <0> (ø)	⬇️
.../org/apache/dubbo/config/AbstractMethodConfig.java	94% <75%> (ø)	0 <0> (ø)	⬇️
...g/apache/dubbo/config/AbstractInterfaceConfig.java	75.08% <87.5%> (+0.33%)	0 <0> (ø)	⬇️
...onfig/spring/extension/SpringExtensionFactory.java	80.48% <0%> (-4.88%)	0% <0%> (ø)
.../dubbo/remoting/transport/netty4/NettyChannel.java	61.17% <0%> (-4.71%)	0% <0%> (ø)
.../apache/dubbo/remoting/transport/AbstractPeer.java	60.86% <0%> (-4.35%)	0% <0%> (ø)
...c/main/java/org/apache/dubbo/rpc/RpcException.java	82.75% <0%> (-3.45%)	0% <0%> (ø)
... and 8 more

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[zonghaishang]

It looks good

[khanimteyaz]

@zonghaishang thanks a lot. Appreciate your time and merging it to master.