chore: refine the hg-style.xml specification

[msgui]

Purpose of the PR

subtask of #2435

Main Changes

👉: https://github.com/apache/incubator-hugegraph/wiki/HugeGraph-Code-Style-Guide
Add the option 'BLANK_LINES_AFTER_CLASS_HEADER' with a value of 1.

Verifying these changes

• Trivial rework / code cleanup without any test coverage. (No Need)
• Already covered by existing tests, such as (please modify tests here).
• Need tests and can be verified as follows:
  • xxx

Does this PR potentially affect the following parts?

• Nope
• Dependencies (add/update license info)
• Modify configurations
• The public API
• Other affects (typed here)

Documentation Status

• Doc - TODO
• Doc - Done
• Doc - No Need

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (1d4532c) 66.23% compared to head (01f4ff0) 63.85%.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2436      +/-   ##
============================================
- Coverage     66.23%   63.85%   -2.39%     
  Complexity      828      828              
============================================
  Files           511      511              
  Lines         42597    42597              
  Branches       5942     5942              
============================================
- Hits          28215    27200    -1015     
- Misses        11566    12652    +1086     
+ Partials       2816     2745      -71     

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