Add -Wconversion flag to protect future developments (backport #1053)

[mergify]

When working on joint_limits, I faced an issue with a rclcpp::Duration that I constructed using seconds and nanoseconds, but by mistake used a float 0.005 for the seconds. Since the awaited arguments are ints, the float conversion led to a NULL duration which I did not realize for a too long time.

There was no compilation warning, as -Wall does not include -Wconversion, supposedly to avoid too many warnings.
With that flag the warning looks like this

rolling-ctrl-ws/src/ros2_control/joint_limits/test/test_simple_joint_limiter.cpp:224:29: warning: conversion from ‘double’ to ‘int32_t’ {aka ‘int’} changes value from ‘5.0000000000000001e-3’ to ‘0’ [-Wfloat-conversion]
  224 |     rclcpp::Duration period(0.005, 0);

I tested in ros_control package to add -Wconversion compilation flag which created only 2 warnings, that could be easily fixed with explicit cast.

Hence, for protecting future developments from risky mistakes with conversions, I suggest to add this flag in all packages of the repo. I will provide a similar PR for ros2_controllers that were definitively affected by exactly the same Time-at-zero issue.

---

This is an automatic backport of pull request #1053 done by [Mergify](https://mergify.com).

[mergify]

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Changes to be committed:
	modified:   hardware_interface/src/component_parser.cpp

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   controller_interface/CMakeLists.txt
	both modified:   controller_manager/CMakeLists.txt
	both modified:   hardware_interface/CMakeLists.txt
	both modified:   joint_limits/CMakeLists.txt
	both modified:   transmission_interface/CMakeLists.txt
	both modified:   transmission_interface/test/random_generator_utils.hpp

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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 62.55%. Comparing base (8bf8a6c) to head (fa2cee1).
Report is 1 commits behind head on humble.

Additional details and impacted files

@@            Coverage Diff             @@
##           humble    #1815      +/-   ##
==========================================
- Coverage   62.57%   62.55%   -0.02%     
==========================================
  Files         108      108              
  Lines       12025    12027       +2     
  Branches     8129     8132       +3     
==========================================
- Hits         7525     7524       -1     
- Misses        880      882       +2     
- Partials     3620     3621       +1     

Flag	Coverage Δ
unittests	62.55% <100.00%> (-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/component_parser.cpp	91.88% <100.00%> (+0.07%)	⬆️

... and 1 file with indirect coverage changes