[#372] Enhance coverage script to generate branch coverage reports for workspace and individual components

[Afshankk]

Notes for Reviewer

This PR enhances the coverage script (internal/scripts/generate-cov-report.sh) to support branch coverage reporting and per-component coverage generation.

Key Changes:

• Added --branches flag to enable branch coverage in reports (for both Rust and C++)
• Added --component <name> flag to generate coverage for specific components (can be used multiple times)
• Updated show_overview() and show_report() functions to support branch coverage filtering
• Modified generate_rust_profile() to support testing individual components via cargo test -p
• Enhanced generate_report() to dynamically build ignore patterns for component filtering
• Updated GitHub Actions workflow to include branch coverage in CI/CD pipeline
• Improved help documentation with usage examples

Testing:
The script now supports multiple usage patterns:

1. Full workspace with branch coverage: ./generate-cov-report.sh --full --branches
2. Single component: ./generate-cov-report.sh --generate --html --component iceoryx2-cal
3. Multiple components: ./generate-cov-report.sh --html --component iceoryx2 --component iceoryx2-cal --branches

Documentation:

1. Updated release notes in doc/release-notes/iceoryx2-unreleased.md under Workflow section
2. Enhanced script help with examples

Pre-Review Checklist for the PR Author

• Add sensible notes for the reviewer
• PR title is short, expressive and meaningful
• Consider switching the PR to a draft (Convert to draft)
• Relevant issues are linked in the References section
• Branch follows the naming format (iox2-372)
• Commits messages are according to this guideline
• Commit messages have the issue ID ([#372])
• Tests follow the best practice for testing
• Changelog updated in the unreleased section including API breaking changes
• Assign PR to reviewer
• All checks have passed (except task-list-completed)

References

Closes #372

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.80%. Comparing base (76c810e) to head (df09280).
⚠️ Report is 17 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1350      +/-   ##
==========================================
- Coverage   77.81%   77.80%   -0.02%     
==========================================
  Files         412      412              
  Lines       39008    39008              
  Branches     1256     1256              
==========================================
- Hits        30354    30350       -4     
- Misses       7621     7625       +4     
  Partials     1033     1033              

Flag	Coverage Δ
CPP	68.04% <ø> (ø)
Rust	77.65% <ø> (-0.02%)	⬇️

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see 5 files with indirect coverage changes

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[dkroenke]

I'm not sure if this flag has any effect because we see the branch coverage already in the existing report for the C++ Code and this flag is in gcovr marked as deprecated and affects only the txt output.
When comparing the reports where the flag is enabled/disabled there seems to be no difference.

[dkroenke]

The branch coverage can be enabled by default so that the additional parameter here is not needed.

[dkroenke]

I tried this command and it generates an empty report for the Rust code. The target folder was cleaned up before. It could be maybe related to the handling of GRCOV_IGNORES in the generate_report() function.
The Rust build and test respects the component setting correctly.