moveit_ros_benchmarks: Require cxx_std_20 compile feature

[traversaro]

Description

Since #1539 the moveit_ros_benchmarks library uses internally the designated initializers feature, that is only available in C++ 20 (see https://en.cppreference.com/w/cpp/language/aggregate_initialization.html#Designated_initializers).

It seems that GCC and Clang permits to use designated initializers even in C++17 mode, but MSVC instead raise an error like:

2025-06-22T00:10:29.7938610Z  │ │ %SRC_DIR%\ros-kilted-moveit-ros-benchmarks\src\work\src\BenchmarkExecutor.cpp(811,9): error C7555: use of designated initializers requires at least '/std:c++20' [%SRC_DIR%\build\moveit_ros_benchmarks.vcxproj]
2025-06-22T00:10:29.8041863Z  │ │ %SRC_DIR%\ros-kilted-moveit-ros-benchmarks\src\work\src\BenchmarkExecutor.cpp(906,11): error C7555: use of designated initializers requires at least '/std:c++20' [%SRC_DIR%\build\moveit_ros_benchmarks.vcxproj]

see https://github.com/RoboStack/ros-kilted/actions/runs/15800837297/job/44538772389#step:6:3639 .

This PR fixes this by requesting the use at least of C++ 20 features with target_compile_features(moveit_ros_benchmarks PRIVATE cxx_std_20).

Checklist

• Required by CI: Code is auto formatted using clang-format
• Extend the tutorials / documentation reference
• Document API changes relevant to the user in the MIGRATION.md notes
• Create tests, which fail without this PR reference
• Include a screenshot if changing a GUI
• While waiting for someone to review your request, please help review another open pull request to support the maintainers

[codecov]

Codecov Report

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Additional details and impacted files

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  Files           ?      720           
  Lines           ?    62713           
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  Hits            ?    28974           
  Misses          ?    33572           
  Partials        ?      167           

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