[#264] update connections

[elfenpiff]

Notes for Reviewer

This PR adds the update_connections call to the C++ API. This call is required to connect new subscriber and deliver the history. It is usually done when a sample is published but when no samples are published, a manual call is required.

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 #264

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.44%. Comparing base (5bd86ec) to head (d37104a).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #384      +/-   ##
==========================================
- Coverage   79.48%   79.44%   -0.04%     
==========================================
  Files         193      193              
  Lines       22716    22716              
==========================================
- Hits        18055    18046       -9     
- Misses       4661     4670       +9     

Files with missing lines	Coverage Δ
iceoryx2/src/port/publisher.rs	84.79% <ø> (ø)

... and 7 files with indirect coverage changes