joint_state_broadcaster to use realtime tools (backport #308)

[mergify]

This is an automatic backport of pull request #308 done by Mergify.
Cherry-pick of 1363baf has failed:

On branch mergify/bp/galactic/pr-308
Your branch is up to date with 'origin/galactic'.

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Changes to be committed:
	modified:   joint_state_broadcaster/CMakeLists.txt
	modified:   joint_state_broadcaster/include/joint_state_broadcaster/joint_state_broadcaster.hpp
	modified:   joint_state_broadcaster/package.xml

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   joint_state_broadcaster/src/joint_state_broadcaster.cpp
	both modified:   joint_state_broadcaster/test/test_joint_state_broadcaster.cpp

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

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[bmagyar]

@zultron could you please give this a quick check?