chore: Simplified the Env class in apollo-portal that links to Env enum in apollo-core

[DiegoKrupitza]

Since the Env class in portal/environment is a class representation of
the enum Env in the apollo core project I linked them better together.
This means if important changes happen in the enum it is automatically
reflected to the class representation.

Additionall I simplified the transformEnv method inside the Env class.
The switch will be never reached since all those values are already
matched in the Env.valueOf(envName).

Further more I added more javadoc and tests to boost up the coverage

What's the purpose of this PR

Make the link between the class representation and the enum stronger, simplify the code and boost the test covergae

Which issue(s) this PR fixes:

None

Brief changelog

XXXXX

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• Update the CHANGES log.

[codecov-commenter]

Codecov Report

Merging #4011 (1781809) into master (8484178) will increase coverage by 0.08%.
The diff coverage is 92.64%.

@@             Coverage Diff              @@
##             master    #4011      +/-   ##
============================================
+ Coverage     51.46%   51.55%   +0.08%     
- Complexity     2524     2529       +5     
============================================
  Files           484      484              
  Lines         14798    14806       +8     
  Branches       1532     1533       +1     
============================================
+ Hits           7616     7633      +17     
+ Misses         6652     6646       -6     
+ Partials        530      527       -3     

Impacted Files	Coverage Δ
...ctrip/framework/apollo/portal/environment/Env.java	92.75% <92.64%> (+23.90%)	⬆️
...work/apollo/biz/message/DatabaseMessageSender.java	50.00% <0.00%> (-14.59%)	⬇️
...work/apollo/biz/message/ReleaseMessageScanner.java	85.52% <0.00%> (+2.63%)	⬆️

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[DiegoKrupitza]

Quick question: why does my pull request effect .../apollo/internals/RemoteConfigLongPollService.java and ...ervice/service/ReleaseMessageServiceWithCache.java? I did not change/created any classes that have any relationship to those two 🤔

CC:
@kezhenxu94
@Anilople

[kezhenxu94]

Quick question: why does my pull request effect .../apollo/internals/RemoteConfigLongPollService.java and ...ervice/service/ReleaseMessageServiceWithCache.java? I did not change/created any classes that have any relationship to those two 🤔

CC: @kezhenxu94 @Anilople

@DiegoKrupitza might be a bug of the coverage tool, because when you click the class, it just jumps to Env class

[DiegoKrupitza]

Quick question: why does my pull request effect .../apollo/internals/RemoteConfigLongPollService.java and ...ervice/service/ReleaseMessageServiceWithCache.java? I did not change/created any classes that have any relationship to those two 🤔
CC: @kezhenxu94 @Anilople

@DiegoKrupitza might be a bug of the coverage tool, because when you click the class, it just jumps to Env class

@kezhenxu94 Ok good to know! For a sec I thought I broke smth 😰

[Anilople]

Thanks the pull request！

This is the reason of why exists a Env in apollo-portal module #2827 (comment)

Code will be review later soon.

[DiegoKrupitza]

Every suggestion made by @Anilople should now be implemented

[Anilople]

LGTM