feat: add IISLogRecord and legacy parsing

[PrzemyslawKlys]

Summary

• introduce IISLogRecord with user-friendly property names
• allow legacy IISLogEvent parsing via ParserEngine and PowerShell cmdlet switch
• update parser, cmdlet and tests for new record support

Testing

• dotnet build IISParser.sln
• dotnet test IISParser.sln

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https://chatgpt.com/codex/tasks/task_e_68a9d80ea19c832eb2283434c4bd6ed5

[codecov-commenter]

Codecov Report

❌ Patch coverage is 89.83051% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.40%. Comparing base (4ae247e) to head (b2057f3).

Files with missing lines	Patch %	Lines
IISParser/ParserEngine.cs	83.78%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #17      +/-   ##
==========================================
+ Coverage   82.80%   86.40%   +3.60%     
==========================================
  Files           4        5       +1     
  Lines         157      206      +49     
  Branches       32       35       +3     
==========================================
+ Hits          130      178      +48     
  Misses         20       20              
- Partials        7        8       +1     

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