[Diagnostics] Add diagnostics of execution time and periodicity of the controllers and controller_manager

[saikishor]

This PR aims to add diagnostics to the controller_manager and the loaded controllers regarding their periodicity and execution time.

Needs: ros-controls/realtime_tools#192

The diagnostics should kinda look like the following screenshots (The following are only to look at the summary):

[christophfroehlich]

I successfully tested the new diagnostics with the demos (synchronous controllers), but as I haven't used them much a note for myself (would have been valid with #1764 already)

• per default, /diagnostics is sent with 1Hz by the Updater, we don't set a different value in the CM's constructor
• diagnostics_updater_ lives in a non RT-thread, and so do also the callback methods.

One comment as we are adding more and more parameters: Would it make sense to use generate_parameter_library also for the CM? I think we can't use it for the per-controller parameters because maps do not work well here, and there is no way to "namespace" parameters with GPL. But for the others?

[saikishor]

@christophfroehlich yes, I thought of using the GPL for this, but I wanted to see your opinion here before taking any decision. I'm open to having this

[codecov]

Codecov Report

Attention: Patch coverage is 73.87755% with 64 lines in your changes missing coverage. Please review.

Project coverage is 87.59%. Comparing base (2b22d0c) to head (18e67f6).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
controller_manager/src/controller_manager.cpp	58.57%	49 Missing and 9 partials ⚠️
...ontroller_manager/test/test_controller_manager.cpp	93.75%	5 Missing ⚠️
...roller_interface/src/controller_interface_base.cpp	94.11%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1871      +/-   ##
==========================================
- Coverage   87.83%   87.59%   -0.25%     
==========================================
  Files         121      122       +1     
  Lines       12555    12766     +211     
  Branches     1131     1146      +15     
==========================================
+ Hits        11028    11182     +154     
- Misses       1108     1155      +47     
- Partials      419      429      +10     

Flag	Coverage Δ
unittests	87.59% <73.87%> (-0.25%)	⬇️

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

Files with missing lines	Coverage Δ
...controller_interface/controller_interface_base.hpp	92.30% <ø> (ø)
.../include/controller_manager/controller_manager.hpp	100.00% <ø> (ø)
...ger/include/controller_manager/controller_spec.hpp	100.00% <100.00%> (ø)
controller_manager/src/ros2_control_node.cpp	76.08% <100.00%> (ø)
...ler_manager/test/test_hardware_management_srvs.cpp	98.57% <100.00%> (+0.01%)	⬆️
...roller_interface/src/controller_interface_base.cpp	82.47% <94.11%> (-2.90%)	⬇️
...ontroller_manager/test/test_controller_manager.cpp	96.10% <93.75%> (-0.15%)	⬇️
controller_manager/src/controller_manager.cpp	76.61% <58.57%> (-1.69%)	⬇️

[christophfroehlich]

LGTM. For reference, the doc page looks the following:

[bmagyar]

Generally looks really good but I posted a few questions sir

[bmagyar]

thank you!