Add notification about the usage of <rclcpp/rclcpp.hpp>. (backport #7113)

[mergify]

Description

closes #7095

Fixes # (issue)

Did you use Generative AI?

Yes, Claude Fable 5

Additional Information

---

This is an automatic backport of pull request #7113 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of e8142b2 has failed:

On branch mergify/bp/kilted/pr-7113
Your branch is up to date with 'origin/kilted'.

You are currently cherry-picking commit e8142b2.
  (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:   conf.py
	modified:   source/Tutorials/Advanced/FastDDS-Configuration.rst
	modified:   source/Tutorials/Advanced/Reading-From-A-Bag-File-CPP.rst
	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/MyRobotDriver.hpp
	modified:   source/Tutorials/Advanced/Simulators/Webots/Setting-Up-Simulation-Webots-Advanced.rst
	modified:   source/Tutorials/Advanced/Topic-Statistics-Tutorial/Topic-Statistics-Tutorial.rst
	modified:   source/Tutorials/Beginner-Client-Libraries/Custom-ROS2-Interfaces.rst
	modified:   source/Tutorials/Beginner-Client-Libraries/Using-Parameters-In-A-Class-CPP.rst
	modified:   source/Tutorials/Beginner-Client-Libraries/Writing-A-Simple-Cpp-Publisher-And-Subscriber.rst
	modified:   source/Tutorials/Beginner-Client-Libraries/Writing-A-Simple-Cpp-Service-And-Client.rst
	modified:   source/Tutorials/Demos/Content-Filtering-Subscription.rst
	modified:   source/Tutorials/Intermediate/Monitoring-For-Parameter-Changes-CPP.rst
	modified:   source/Tutorials/Intermediate/RViz/Marker-Points-and-Lines/Marker-Points-and-Lines.rst
	modified:   source/Tutorials/Intermediate/RViz/Marker-Sending-Basic-Shapes/Marker-Sending-Basic-Shapes.rst
	modified:   source/Tutorials/Intermediate/Tf2/Adding-A-Frame-Cpp.rst
	modified:   source/Tutorials/Intermediate/Tf2/Using-Stamped-Datatypes-With-Tf2-Ros-MessageFilter.rst
	modified:   source/Tutorials/Intermediate/Tf2/Writing-A-Tf2-Broadcaster-Cpp.rst
	modified:   source/Tutorials/Intermediate/Tf2/Writing-A-Tf2-Listener-Cpp.rst
	modified:   source/Tutorials/Intermediate/Tf2/Writing-A-Tf2-Static-Broadcaster-Cpp.rst
	modified:   source/Tutorials/Intermediate/URDF/Using-URDF-with-Robot-State-Publisher-cpp.rst
	modified:   source/Tutorials/Intermediate/Using-Node-Interfaces-Template-Class.rst
	modified:   source/Tutorials/Intermediate/Writing-an-Action-Server-Client/Cpp.rst
	new file:   source/_internal/Rclcpp-Convenience-Header-Note.rst

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   source/ROS-Framework/client-libraries/Working-with-Client-Libraries/Single-Package-Define-And-Use-Interface.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

[fujitatomoya]

@ahcorde requesting your approval since i resolved some conflicts.

[github-actions]

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