optimize: optimize the reflection operation in class SerializerServiceLoader

[wangliang181230]

• I have registered the PR changes.

Ⅰ. Describe what this PR did

optimize: Optimize the reflection operation in class SerializerServiceLoader

Ⅱ. Does this pull request fix one issue?

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

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov]

Codecov Report

Attention: Patch coverage is 71.42857% with 2 lines in your changes missing coverage. Please review.

Project coverage is 52.22%. Comparing base (8288a57) to head (8a2fcd7).
Report is 1 commits behind head on 2.x.

Files	Patch %	Lines
...seata/core/serializer/SerializerServiceLoader.java	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x    #6780      +/-   ##
============================================
- Coverage     52.36%   52.22%   -0.15%     
+ Complexity     6306     6293      -13     
============================================
  Files          1064     1064              
  Lines         37179    37181       +2     
  Branches       4415     4415              
============================================
- Hits          19470    19418      -52     
- Misses        15785    15846      +61     
+ Partials       1924     1917       -7     

Files	Coverage Δ
...a/org/apache/seata/common/util/ReflectionUtil.java	73.11% <100.00%> (+0.59%)	⬆️
...seata/core/serializer/SerializerServiceLoader.java	60.00% <33.33%> (+6.87%)	⬆️

... and 7 files with indirect coverage changes

[funky-eyes]

LGTM