(moveit_py) Add Trajectory Execution Manager (backport #2406)

[mergify]

This is an automatic backport of pull request #2406 done by Mergify.
Cherry-pick of 76a488b has failed:

On branch mergify/bp/iron/pr-2406
Your branch is up to date with 'origin/iron'.

You are currently cherry-picking commit 76a488b54.
  (fix conflicts and run "git cherry-pick --continue")
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Changes to be committed:
	modified:   moveit_py/CMakeLists.txt
	modified:   moveit_py/moveit/core/controller_manager.pyi
	modified:   moveit_py/moveit/planning.pyi
	modified:   moveit_py/src/moveit/moveit_core/controller_manager/controller_manager.cpp
	modified:   moveit_py/src/moveit/moveit_ros/moveit_cpp/moveit_cpp.cpp
	new file:   moveit_py/src/moveit/moveit_ros/trajectory_execution_manager/trajectory_execution_manager.cpp
	new file:   moveit_py/src/moveit/moveit_ros/trajectory_execution_manager/trajectory_execution_manager.h

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   moveit_py/src/moveit/planning.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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[github-actions]

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