feat: option to sort enum member in declaring order

[yufeih]

Introduces an enumSortOrder option to specify enum member sort options:

• alphabetic (default): Sort enum members in alphabetic order.
• declaringOrder: Sort enum members in the order as they are declared in the source code.

fixes #2285

[codecov]

Codecov Report

Patch coverage: 91.66% and project coverage change: -0.01% ⚠️

Comparison is base (f698eac) 77.57% compared to head (a24c1d3) 77.57%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9093      +/-   ##
==========================================
- Coverage   77.57%   77.57%   -0.01%     
==========================================
  Files         592      592              
  Lines       24608    24614       +6     
==========================================
+ Hits        19090    19094       +4     
- Misses       5518     5520       +2     

Files Changed	Coverage Δ
src/Docfx.Dotnet/YamlViewModelExtensions.cs	85.90% <87.50%> (-0.26%)	⬇️
src/Docfx.Dotnet/DotnetApiCatalog.cs	67.79% <100.00%> (+0.55%)	⬆️
...fx.Dotnet/ExtractMetadata/ExtractMetadataConfig.cs	100.00% <100.00%> (ø)
...fx.Dotnet/ExtractMetadata/ExtractMetadataWorker.cs	80.71% <100.00%> (ø)
src/Docfx.Dotnet/MetadataJsonConfig.cs	95.00% <100.00%> (+0.26%)	⬆️

... and 1 file with indirect coverage changes

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