Add AsyncFunctionHandlerParams initialization through ROS parameters (backport #402)

[mergify]

I've added a way to initialize the current parameter from the ROS nodes directly, much easier when using with nodes and controllers

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This is an automatic backport of pull request #402 done by Mergify.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 64.86486% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.65%. Comparing base (471295c) to head (b79332d).
⚠️ Report is 25 commits behind head on jazzy.

Files with missing lines	Patch %	Lines
.../include/realtime_tools/async_function_handler.hpp	56.66%	5 Missing and 8 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            jazzy     #413      +/-   ##
==========================================
- Coverage   85.63%   84.65%   -0.98%     
==========================================
  Files          19       19              
  Lines        1448     1499      +51     
  Branches      128      146      +18     
==========================================
+ Hits         1240     1269      +29     
- Misses        124      133       +9     
- Partials       84       97      +13     

Flag	Coverage Δ
unittests	84.65% <64.86%> (-0.98%)	⬇️

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Files with missing lines	Coverage Δ
...ealtime_tools/test/test_async_function_handler.cpp	100.00% <100.00%> (+1.31%)	⬆️
.../include/realtime_tools/async_function_handler.hpp	74.87% <56.66%> (-7.40%)	⬇️

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