Allow for trailing comma in global.json parsing

[AndyGerlicher]

Currently the DotNetComponentDetector fails for trailing commas parsing global.json. An example I hit:

{
  // Defines version of MSBuild project SDKs to use
  // https://docs.microsoft.com/en-us/visualstudio/msbuild/how-to-use-project-sdk?view=vs-2017#how-project-sdks-are-resolved
  // https://docs.microsoft.com/en-us/dotnet/core/tools/global-json#globaljson-schema
  "msbuild-sdks": {
    "Microsoft.Build.Traversal": "4.1.82",
    "Microsoft.Build.NoTargets": "3.7.134"
  },
}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.2%. Comparing base (07d23ff) to head (ef76890).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #1545   +/-   ##
=====================================
  Coverage   90.2%   90.2%           
=====================================
  Files        423     423           
  Lines      35452   35476   +24     
  Branches    2207    2209    +2     
=====================================
+ Hits       31997   32020   +23     
  Misses      3001    3001           
- Partials     454     455    +1     

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[Copilot]

Pull Request Overview

This PR fixes a bug where the DotNetComponentDetector failed to parse global.json files containing trailing commas. The fix enables trailing comma support in the JSON parser, and adds test coverage for this scenario.

• Added AllowTrailingCommas = true to the JSON parser options used for global.json parsing
• Added a new test case TestDotNetDetectorGlobalJsonWithTrailingCommas_ReturnsSDKVersion to verify the fix

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/Microsoft.ComponentDetection.Detectors/dotnet/DotNetComponentDetector.cs	Updated JsonDocumentOptions to allow trailing commas in addition to existing comment handling support
test/Microsoft.ComponentDetection.Detectors.Tests/DotNetComponentDetectorTests.cs	Added test case to verify global.json files with trailing commas are parsed successfully

[github-actions]

👋 Hi! It looks like you modified some files in the Detectors folder.
You may need to bump the detector versions if any of the following scenarios apply:

• The detector detects more or fewer components than before
• The detector generates different parent/child graph relationships than before
• The detector generates different devDependencies values than before

If none of the above scenarios apply, feel free to ignore this comment 🙂