feat(5626): Python TRX/Cobertura HTML report; run-test-case.sh; unit-test w…

[OMpawar-21]

Summary

Adds local and CI support for unit tests with coverage, and generates an HTML report from TRX + Cobertura using a Python script (no ReportGenerator / .NET 8+ requirement for HTML).

Changes

• Scripts/run-unit-test-case.sh — Clears TestResults, runs dotnet test on the test project with TRX logging and Coverlet (XPlat code coverage).
• Scripts/run-test-case.sh — Runs tests on the solution, finds coverage.cobertura.xml, invokes Scripts/generate_test_report.py to write Coverage-<date>/index.html under the test project’s TestResults folder.
• Scripts/generate_test_report.py — Standard-library-only TRX + Cobertura parser; builds HTML (summary, pass rate, coverage tables, tests by class file). Duration removed from the report UI.
• .github/workflows/unit-test.yml — Runs run-unit-test-case.sh on Windows for push and pull_request (no dorny/test-reporter).
• Contentstack.Utils.Tests.csproj — Removed duplicate Reference to a built DLL; aligned test package versions (e.g. Test SDK, coverlet, Newtonsoft) with the management SDK pattern where applicable.

How to verify

1. From repo root: bash Scripts/run-test-case.sh
2. Open the printed path to .../TestResults/Coverage-Contentstack-DotNet-Test-Case-<date>/index.html in a browser.
3. Confirm the Unit Test workflow passes on the PR.

Notes

• No NuGet / library version bump — test and tooling only; Contentstack.Utils API and package version unchanged.
• HTML reporting is optional for local use; CI uses the lighter unit-test script and still produces TRX + Cobertura for downstream tools.