Bump C++ version to C++20

[christophfroehlich]

Description

https://discourse.openrobotics.org/t/ros-2-lyrical-c-version/52551

Needs ros-controls/ros2_control_cmake#28

Is this user-facing behavior change?

hopefully not

Did you use Generative AI?

no

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.68%. Comparing base (81e94e8) to head (851b24c).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #119   +/-   ##
=======================================
  Coverage   77.68%   77.68%           
=======================================
  Files           6        6           
  Lines         457      457           
  Branches       46       46           
=======================================
  Hits          355      355           
  Misses         70       70           
  Partials       32       32           

Flag	Coverage Δ
unittests	77.68% <ø> (ø)

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