test(union): add full examples for union in list/map

[Kybxd]

• close union: support vertical predefined-union list #281

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 74.40%. Comparing base (eaf79c5) to head (ad17842).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/confgen/table_parser.go	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #321      +/-   ##
==========================================
+ Coverage   74.37%   74.40%   +0.03%     
==========================================
  Files          83       83              
  Lines        8372     8374       +2     
==========================================
+ Hits         6227     6231       +4     
+ Misses       1577     1576       -1     
+ Partials      568      567       -1     

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