[#213] increase test container coverage

[elfenpiff]

Notes for Reviewer

Pre-Review Checklist for the PR Author

1. Add sensible notes for the reviewer
2. PR title is short, expressive and meaningful
3. Relevant issues are linked in the References section
4. Every source code file has a copyright header with SPDX-License-Identifier: Apache-2.0 OR MIT
5. Branch follows the naming format (iox2-123-introduce-posix-ipc-example)
6. Commits messages are according to this guideline
   • Commit messages have the issue ID ([#123] Add posix ipc example)
   • Commit author matches Eclipse Contributor Agreement (and ECA is signed)
7. Tests follow the best practice for testing
8. Changelog updated in the unreleased section including API breaking changes
9. Assign PR to reviewer
10. All checks have passed (except task-list-completed)

Checklist for the PR Reviewer

• Commits are properly organized and messages are according to the guideline
• Unit tests have been written for new behavior
• Public API is documented
• PR title describes the changes

Post-review Checklist for the PR Author

1. All open points are addressed and tracked via issues

References

Relates to #213

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 80.03%. Comparing base (c1accf9) to head (e12486f).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #218      +/-   ##
==========================================
+ Coverage   79.59%   80.03%   +0.43%     
==========================================
  Files         183      183              
  Lines       20420    20423       +3     
==========================================
+ Hits        16254    16346      +92     
+ Misses       4166     4077      -89     

Files	Coverage Δ
iceoryx2-bb/container/src/byte_string.rs	99.09% <100.00%> (+9.30%)	⬆️
iceoryx2-bb/container/src/semantic_string.rs	87.64% <100.00%> (+11.84%)	⬆️
iceoryx2-bb/posix/src/directory.rs	63.82% <100.00%> (ø)
iceoryx2-bb/posix/src/group.rs	71.92% <0.00%> (ø)

... and 12 files with indirect coverage changes