feat: Implement vertical aggregation with consistency validation

[Kybxd]

This PR implements a vertical aggregation feature with the following key changes:

Core Changes

1. Added aggregate field property (bool aggregate = 21 in FieldProp) to enable vertical aggregation for incell list/map fields
2. Added data consistency validation that throws E2023 error when conflicting values are found in different rows

Behavior Changes

• Default behavior: Data consistency validation (non-aggregating) - validates that values for the same key are identical across rows
• Aggregate mode: Enabled via aggregate:true - allows vertical aggregation of values for the same key

Vertical Aggregation Scope Limitations

• Only supports incell list/map fields - horizontal and vertical layout fields do not support aggregation
• Incell struct/union/scalar fields use consistency validation only

Implementation Details

• Uses msg.NewField() to create new values instead of directly modifying existing ones
• Compares values using Equal() method for consistency checking
• Supports incremental aggregation for maps/lists when aggregate=true

This feature enhances data parsing flexibility for scenarios requiring vertical data aggregation while maintaining data integrity through consistency validation.

[codecov]

Codecov Report

❌ Patch coverage is 70.05650% with 53 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.98%. Comparing base (5a4e7fc) to head (b3ed9b7).

Files with missing lines	Patch %	Lines
internal/confgen/table_parser.go	68.60%	20 Missing and 7 partials ⚠️
internal/confgen/document_parser.go	50.00%	9 Missing and 3 partials ⚠️
internal/confgen/util.go	41.66%	7 Missing ⚠️
internal/confgen/parser.go	82.85%	4 Missing and 2 partials ⚠️
internal/localizer/i18n/i18n.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #395      +/-   ##
==========================================
- Coverage   74.05%   73.98%   -0.08%     
==========================================
  Files          87       87              
  Lines        8819     8879      +60     
==========================================
+ Hits         6531     6569      +38     
- Misses       1718     1742      +24     
+ Partials      570      568       -2     

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