optimize: support configuration metadata read from environment variables

[slievrly]

Signed-off-by: slievrly slievrly@163.com

• I have registered the PR changes.

Ⅰ. Describe what this PR did

optimize: support configuration metadata read from environment variables

After seata-server SpringBoot adaptation, the metadata configuration file is changed from registry.conf to application.yml.
This change causes `ConfigurationFactory#CURRENT_FILE_INSTANCE` to be proxyed by the `SpringBootConfigurationProvider`. 
It lead to fail to `AbstractConfiguration#getConfig` logical priority reads the value of environment variables. 
As immutable infrastructure, Seata-Server Docker should prioritize reading environment variables to reduce intrusion into container images.

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Seata-Server SpringBoot 适配改造后，元数据配置文件由registry.conf 变更为 application.yml。这个变更导致了ConfigurationFactory#CURRENT_FILE_INSTANCE 被 SpringBootConfigurationProvider 所代理。这将导致未按照AbstractConfiguration#getConfig 的逻辑优先读取环境变量的值。

Seata-Server docker作为不可变基础设施，应优先读取环境变量，减少对容器镜像改造的侵入性。

Ⅱ. Does this pull request fix one issue?

ref #3869

Ⅲ. Why don't you add test cases (unit test/integration test)?

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov-commenter]

Codecov Report

Merging #4359 (2cd7036) into develop (732f287) will decrease coverage by 0.07%.
The diff coverage is 44.44%.

@@              Coverage Diff              @@
##             develop    #4359      +/-   ##
=============================================
- Coverage      48.94%   48.87%   -0.08%     
+ Complexity      3952     3949       -3     
=============================================
  Files            733      733              
  Lines          24968    24974       +6     
  Branches        3088     3090       +2     
=============================================
- Hits           12220    12205      -15     
- Misses         11453    11475      +22     
+ Partials        1295     1294       -1     

Impacted Files	Coverage Δ
...gure/provider/SpringBootConfigurationProvider.java	48.27% <40.00%> (+0.06%)	⬆️
...e/src/main/java/io/seata/config/Configuration.java	45.45% <50.00%> (+2.59%)	⬆️
...er/src/main/java/io/seata/server/ServerRunner.java	50.00% <0.00%> (-15.39%)	⬇️
...o/seata/server/coordinator/DefaultCoordinator.java	47.08% <0.00%> (-5.48%)	⬇️
...very/registry/zk/ZookeeperRegisterServiceImpl.java	61.76% <0.00%> (+0.73%)	⬆️