Add Codecov Test Analytics

[katia-sentry]

This PR sets up Codecov Test Analytics, which enhances this project's existing Codecov coverage PR notification with details about failing, flaky, and slow tests. More details can be found here, and below is an example screenshot.

Changes

1. Updated test run command to include --junitxml=test-results.xml so Codecov can parse test analytics.
2. Added codecov/test-results-action@v1 step to upload the generated test-results.xml for Test Analytics.

Looking forward to your feedback!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.37%. Comparing base (d8c1ae3) to head (0f59804).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1321   +/-   ##
=======================================
  Coverage   99.37%   99.37%           
=======================================
  Files         161      161           
  Lines       21069    21069           
  Branches     3791     3791           
=======================================
  Hits        20938    20938           
  Misses        121      121           
  Partials       10       10           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[caronc]

Looks good, thank you for the PR! 🙏