Add on_set_value_callbacks to State and Command Interface

[saikishor]

This PR opens a possibility to add on_set_value_callback to the State and Command Interfaces, so we can simply add filters or pre-process the data before setting the value. This is helpful when you get references, and when they do not meet certain conditions, you process them and set the right value.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.89%. Comparing base (b87334a) to head (0a0d543).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2365      +/-   ##
==========================================
+ Coverage   88.84%   88.89%   +0.05%     
==========================================
  Files         148      148              
  Lines       16893    16938      +45     
  Branches     1438     1442       +4     
==========================================
+ Hits        15008    15057      +49     
+ Misses       1319     1316       -3     
+ Partials      566      565       -1     

Flag	Coverage Δ
unittests	88.89% <100.00%> (+0.05%)	⬆️

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Files with missing lines	Coverage Δ
...re_interface/include/hardware_interface/handle.hpp	91.59% <100.00%> (+0.68%)	⬆️
hardware_interface/test/test_handle.cpp	98.80% <100.00%> (+0.31%)	⬆️

... and 2 files with indirect coverage changes

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[christophfroehlich]

The changes LGTM, but I'm not really sure if we should add this level of complexity or improve controller chaining with filter plugins to achieve the same. Would like to hear other opinions on that

[saikishor]

The changes LGTM, but I'm not really sure if we should add this level of complexity or improve controller chaining with filter plugins to achieve the same. Would like to hear other opinions on that

I also thought the same at the beginning, but then thinking a bit. I realized that the chaining is completely configuration dependent on the control strategy. If the controller chaining or HW (The owner of the Command and State Interface) expect some kind of filtering, they cannot always expect that the other party always respects that. In that case, the one who is responsible of handling these value will have to filter them again just to make sure, and the approach proposed in the PR makes it simpler by defining the callbacks.

This is one of the things we added to the Kilted roadmap