[tests] Improve test summary to include up to 3 failing unit tests.

[rolfbjarne]

No description provided.

[Copilot]

Pull Request Overview

This PR improves test result summaries by adding detailed information about up to 3 failing unit tests from TRX test result files. The changes introduce a new TRX parser utility that extracts test failure details and integrates it into multiple reporting systems.

• Adds a new TrxParser utility class to parse TRX test result files and extract failed test information
• Updates markdown and HTML report writers to display the first 3 failing tests with truncated names and messages
• Modifies PowerShell test results script to include parsed TRX content in summaries

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tests/common/ParseTrxFile.cs	New TRX parser utility class that extracts failed test information from TRX XML files
tests/xharness/xharness.csproj	Links the new ParseTrxFile.cs into the xharness project
tests/xharness/Jenkins/Reports/MarkdownReportWriter.cs	Integrates TRX parsing to display up to 3 failing unit tests in markdown reports with a Cap string extension method
scripts/create-windows-html-report/create-windows-html-report.csproj	Links ParseTrxFile.cs into the HTML report generator project
scripts/create-windows-html-report/create-windows-html-report.cs	Refactors to use TrxParser instead of inline XML parsing for cleaner code
tools/devops/automation/scripts/TestResults.psm1	Updates PowerShell script to parse and include TRX results in test summaries