Update xunit packages

[martincostello]

Manual update via #3499, but without the unwanted changes to the targets.

[Copilot]

Pull Request Overview

This PR updates xunit-related NuGet packages to their latest versions. The changes focus on upgrading the xunit testing framework and its associated packages.

• Updates xunit.runner.visualstudio from version 3.1.1 to 3.1.2
• Updates xunit.v3 from version 2.0.3 to 3.0.0 (major version upgrade)
• Updates xunit.v3.extensibility.core from version 2.0.3 to 3.0.0 (major version upgrade)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.28%. Comparing base (54e03e9) to head (7e8019f).
Report is 1 commits behind head on master.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3500   +/-   ##
=======================================
  Coverage   94.28%   94.28%           
=======================================
  Files         110      110           
  Lines        3816     3816           
  Branches      722      722           
=======================================
  Hits         3598     3598           
  Misses        218      218           

Flag	Coverage Δ
Linux	94.28% <ø> (ø)
Windows	94.28% <ø> (ø)
macOS	94.28% <ø> (ø)

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