feat(COVERPORT-22): add codecov integration for test coverage

[msu8]

Summary

• Add pytest-cov to dev dependencies and configure coverage settings
• Update GitHub Actions workflow to generate coverage and upload to Codecov with unit-tests flag
• Add codecov.yml with flag analytics and PR comment configuration
• Add push trigger on main branch for baseline coverage

Setup required

• Please add [CODECOV_TOKEN](https://app.codecov.io/gh/konflux-ci/release-service-utils/config/general) as a repository secret in GitHub Settings → Secrets → Actions

[snyk-io]

✅ Snyk checks have passed. No issues have been found so far.

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[codecov-commenter]

Welcome to Codecov 🎉

Once you merge this PR into your default branch, you're all set! Codecov will compare coverage reports and display results in all future pull requests.

Thanks for integrating Codecov - We've got you covered ☂️

[querti]

We've had issues with codecov in our other repos, I don't know if we should enable this until we investigate https://issues.redhat.com/browse/RELEASE-2238

[msu8]

We've had issues with codecov in our other repos, I don't know if we should enable this until we investigate https://issues.redhat.com/browse/RELEASE-2238

Hi, It seems that the dependency update PRs are not running e2e-tests hence why the coverage fails. Could you please share more in #wg-code-coverage Slack - perhaps more teams are having similar issues too.