Replace hard coded dubbo-config-api values and small code optimization

[khanimteyaz]

In this PR I have refactored code to

1. Replace hard coded values from java code to constant. Most of this values where getting used from multiple places so moving to constant avoid development time or run time error for value mismatch.
2. Small refactoring to reduce code volume and use existing JDK provided utility and operation.

Bellow are the java file which has been modified as part of this PR

dubbo-common/src/main/java/org/apache/dubbo/common/Constants.java
dubbo-common/src/main/java/org/apache/dubbo/common/EnvironmentConstants.java
dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/AbstractServiceConfig.java
dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/ApplicationConfig.java
dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/ConfigCenterConfig.java
dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/MethodConfig.java
dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/ModuleConfig.java
dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/ProtocolConfig.java
dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/ProviderConfig.java
dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/ReferenceConfig.java
dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/RegistryConfig.java
dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/ServiceConfig.java

What is the purpose of the change

1. Replace hard coded values from java code to constant. Most of this values where getting used from multiple places so moving to constant avoid development time or run time error for value mismatch.
2. Small refactoring to reduce code volume and use existing JDK provided utility and operation.

Brief changelog

Hard coded value replacement of dubbo-config-api and small refactoring to optimize code size.

Verifying this change

Running UT

Follow this checklist to help us incorporate your contribution quickly and easily:

• Make sure there is a 3107 field for the change (usually before you start working on it). Trivial changes like typos do not require a GITHUB issue. Your pull request should address just this issue, without pulling in other changes - one PR resolves one issue.
• Format the pull request title like [Dubbo-XXX] Fix UnknownException when host config not exist #XXX. Each commit in the pull request should have a meaningful subject line and body.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit-test to verify your logic correction, more mock a little better when cross module dependency exist. If the new feature or significant change is committed, please remember to add integration-test in test module.
• Run mvn clean install -DskipTests=false & mvn clean test-compile failsafe:integration-test to make sure unit-test and integration-test pass.
• If this contribution is large, please follow the Software Donation Guide.

[codecov-io]

Codecov Report

Merging #3108 into master will increase coverage by 0.02%.
The diff coverage is 68.53%.

@@             Coverage Diff              @@
##             master    #3108      +/-   ##
============================================
+ Coverage     63.52%   63.54%   +0.02%     
  Complexity       75       75              
============================================
  Files           652      652              
  Lines         28183    28188       +5     
  Branches       4791     4784       -7     
============================================
+ Hits          17902    17913      +11     
+ Misses         8023     8014       -9     
- Partials       2258     2261       +3

Impacted Files	Coverage Δ	Complexity Δ
...c/main/java/org/apache/dubbo/common/Constants.java	92.85% <ø> (ø)	0 <0> (ø)	⬇️
...va/org/apache/dubbo/config/ConfigCenterConfig.java	31.03% <0%> (ø)	0 <0> (ø)	⬇️
...org/apache/dubbo/config/AbstractServiceConfig.java	95.77% <100%> (ø)	0 <0> (ø)	⬇️
...ava/org/apache/dubbo/config/ApplicationConfig.java	84.33% <100%> (+1.62%)	0 <0> (ø)	⬇️
...ain/java/org/apache/dubbo/config/ModuleConfig.java	86.84% <100%> (ø)	0 <0> (ø)	⬇️
...ain/java/org/apache/dubbo/config/MethodConfig.java	100% <100%> (+1.72%)	0 <0> (ø)	⬇️
...n/java/org/apache/dubbo/config/ProviderConfig.java	95.69% <100%> (ø)	0 <0> (ø)	⬇️
...n/java/org/apache/dubbo/config/RegistryConfig.java	84.21% <40%> (+1.85%)	0 <0> (ø)	⬇️
...n/java/org/apache/dubbo/config/ProtocolConfig.java	75.93% <42.85%> (ø)	0 <0> (ø)	⬇️
...in/java/org/apache/dubbo/config/ServiceConfig.java	53.74% <61.53%> (+0.39%)	0 <0> (ø)	⬇️
... and 12 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d41408e...9ccc95a. Read the comment docs.