Use Pimpl approach for controller and hardware component interfaces

[saikishor]

I've updated with the Pimpl approach to protect the ABI stability in the future

[codecov]

Codecov Report

❌ Patch coverage is 83.93939% with 53 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.45%. Comparing base (eaee0da) to head (62968dc).

Files with missing lines	Patch %	Lines
...are_interface/src/hardware_component_interface.cpp	81.10%	44 Missing and 4 partials ⚠️
...roller_interface/src/controller_interface_base.cpp	94.52%	0 Missing and 4 partials ⚠️
...controller_interface/controller_interface_base.hpp	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2898      +/-   ##
==========================================
- Coverage   89.50%   89.45%   -0.05%     
==========================================
  Files         155      156       +1     
  Lines       18534    18545      +11     
  Branches     1489     1486       -3     
==========================================
+ Hits        16588    16589       +1     
- Misses       1346     1347       +1     
- Partials      600      609       +9     

Flag	Coverage Δ
unittests	89.45% <83.93%> (-0.05%)	⬇️

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

Files with missing lines	Coverage Δ
...ardware_interface/hardware_component_interface.hpp	55.55% <ø> (-19.54%)	⬇️
...controller_interface/controller_interface_base.hpp	90.90% <66.66%> (-0.76%)	⬇️
...roller_interface/src/controller_interface_base.cpp	86.22% <94.52%> (+2.01%)	⬆️
...are_interface/src/hardware_component_interface.cpp	81.10% <81.10%> (ø)

... and 8 files with indirect coverage changes

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[christophfroehlich]

LGTM, thanks!

[Juliaj]

Just for my knowledge, would impl_ ever become null ?

[saikishor]

Nope, it would never, it is initialied in the init or the constructor

[Juliaj]

This is outside the scope of this PR. HardwareComponentInterface explicitly deletes move operations, but we don't have a similar setup in ControllerInterfaceBase. Would this be an issue because unique_ptr is moveable ?

[saikishor]

IIRC, it is done due to the rule of five in C++. We can check if that applies to the controller base class

[Juliaj]

LGTM.