chore: Update xUnit related package version to v3

[filzrev]

This is Draft PR to migrate unit test projects to xUnit v3. (Prev draft PR is #10375)
Currently test execution on VS is unstable

Known issues

1. TestTfmsInParallel: false setting is not works as expected when running tests with VS Test Explorer
   (https://github.com/xunit/visualstudio.xunit/issues/429)

What's changed to this PR

1. Switch xUnit.NET related NuGet packages to v3.

• Verify.Xunit -> Verify.XunitV3
• xunit -> xunit.v3

2. Add additional output log types (*.log/*.ctrf)

3. Change unittest's projects OutputType from LibrarytoExeand Exolicitly setIsTestProject` property

4. Add Microsoft.Testing.Platform related settings
Microsoft.Testing.Platform is alternative unit test execution layers.

6. Add xunit.runner.json config file for test project.

7. Pass TestContext.Current.CancellationToken that require Cancellation token.

8. Modify MetadataCommandTest.cs And add steps to create dummy Directory.Build.props file.
It's required to ignore project directories Directory.Build.props settings

9. Add empty Directory.Build.props file to samples directory

10. Modify CI workflow to use custom seed value to reproduce issue on CI
By default. xUnit determine seed on build time and seed value is different between assemblies.
So to fix seed value. Use github.run_number as a seed value. (It's incremented from 1)

If CI failed by parallel execution related issue.
It can re-run job with using same seed.

11. Add SetBranchNameAttribute that derived from BeforeAfterTestAttribute
When running SeedMarkdown tests before other snapshot tests.
It cause snapshot diffs because GitUtility.cs caching actual branch name.
To simplify environment variable set/restore.
Add custom BeforeAfterTestAttribute for this purpose.

12. Add [assembly:CaptureConsole] attribute to test assemblies.

13. Add ProcessHelper class to invoke external command (e.g. dotnet, docfx).
When using Process.Start to launch external command that stdout.
Running tests is not completed when running tests on Test Explorer.
So I've added utility code to ignoring stdout/stdout.

15. Modify dotnet test --filter Stage=Percy command. to use -- --filter-trait "Stage=Percy"
When TestingPlatformDotnetTestSupport is enabled. dotnet test command's --filter argument is silently ignored. (Same behavior as that reported at https://github.com/microsoft/testfx/issues/4401)
It need modify command to pass additional argument(-- --filter-trait "Stage=Percy")

16. Separate Chromium Headless Shell installation from test steps
Chromium is installed on when running docfx pdf command first time.
It take times and it affects test execution times.
So creating separate chromium install step that is executed before running dotnet test.

https://github.com/dotnet/docfx/pull/10474/files#diff-b803fcb7f17ed9235f1e5cb1fcd2f5d3b2838429d4368ae4c57ce4436577f03fR43-R48

17. Add -nodereuse:false and --no-dependencies parameter to dotnet build command inside tests
After migrated to xUnit v3.
SamplesTest::Extensions dotnet build command takes extra 15 minutes on Windows CI.
It seems relating to https://github.com/dotnet/sdk/issues/9452 so I've added -nodereuse:false parameter to resolve issue.
And adding --no-dependencies parameter to suppress Docfx.App project build during test.

**18. Add dotnet-coverage command related settings.
Currently Microsoft.Testing.Platform don't support coveret-based codecoverage with dotnet test command.