Fix C++20 behavior changes of std::from_chars

[christophfroehlich]

Description

It seems that there is a behavior change in C++20, fixes #3240

This is not reflected in our PR CI jobs, but I was able to reproduce it locally with

colcon build --packages-up-to hardware_interface --cmake-clean-cache --cmake-args -DCMAKE_CXX_STANDARD=20 -DCMAKE_BUILD_TYPE=RelWithDebInfo
colcon test --packages-select hardware_interface

and this PR fixes the test failures.

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GPT 5.3 codex

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.12%. Comparing base (c178e16) to head (0fe20e4).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3244      +/-   ##
==========================================
+ Coverage   89.10%   89.12%   +0.02%     
==========================================
  Files         160      160              
  Lines       19753    19754       +1     
  Branches     1597     1597              
==========================================
+ Hits        17600    17605       +5     
+ Misses       1486     1483       -3     
+ Partials      667      666       -1     

Flag	Coverage Δ
unittests	89.12% <ø> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
hardware_interface/src/lexical_casts.cpp	83.78% <ø> (ø)

... and 4 files with indirect coverage changes

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