Configure Codecov for Per-Directory Coverage Badges

Summary

Related https://github.com/WordPress/performance/issues/1789#issuecomment-2731163370

We need to configure Codecov to display coverage badges for each plugin directory in our repository. This will allow us to track and display code coverage metrics on a per-directory basis, providing more granular insights into our codebase.

Details

Currently, our Codecov setup provides an overall coverage badge for the entire repository. We want to enhance this by showing individual coverage badges for each plugin directory.

Steps to Achieve This

1. Update GitHub Actions Workflow: Modify the .github/workflows/php-test-plugins.yml file to include flags for each plugin when uploading coverage reports to Codecov.

2. Configure Codecov YAML: Create or update the codecov.yml file to define the flags for each plugin directory.

Expected Outcome

• Each plugin directory will have its own coverage badge.
• The badges will be displayed in the README , providing clear visibility into the coverage status of each plugin.

Additional Information

• Reference: Codecov Flags Documentation

cc : @westonruter