Update subscription callback signatures (backport #6005)

[mergify]

Description

Related to ros2/rclcpp#2975, ConstSharedPtr is preferred

Did you use Generative AI?

No

Additional Information

---

This is an automatic backport of pull request #6005 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of bf46139 has failed:

On branch mergify/bp/jazzy/pr-6005
Your branch is up to date with 'origin/jazzy'.

You are currently cherry-picking commit bf46139.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   source/Tutorials/Advanced/Recording-A-Bag-From-Your-Own-Node-CPP.rst
	modified:   source/Tutorials/Advanced/Simulators/Webots/Code/MyRobotDriver.cpp
	modified:   source/Tutorials/Advanced/Simulators/Webots/Code/ObstacleAvoider.cpp
	modified:   source/Tutorials/Advanced/Simulators/Webots/Code/ObstacleAvoider.hpp

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   source/Tutorials/Intermediate/Tf2/Writing-A-Tf2-Broadcaster-Cpp.rst

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[github-actions]

HTML artifacts: https://github.com/ros2/ros2_documentation/actions/runs/20023952419/artifacts/4795686165.

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