[CM] Add message field to the switch_controller service

[saikishor]

As we discussed in the previous WG meeting, I've added the message field to the SwitchControllers service response. This message is also integrated into the CLI

[codecov]

Codecov Report

Attention: Patch coverage is 72.31638% with 49 lines in your changes missing coverage. Please review.

Project coverage is 89.41%. Comparing base (bfbedd2) to head (35dc097).

Files with missing lines	Patch %	Lines
controller_manager/src/controller_manager.cpp	72.31%	40 Missing and 9 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2088      +/-   ##
==========================================
- Coverage   89.59%   89.41%   -0.18%     
==========================================
  Files         139      139              
  Lines       15222    15360     +138     
  Branches     1290     1302      +12     
==========================================
+ Hits        13638    13734      +96     
- Misses       1096     1133      +37     
- Partials      488      493       +5     

Flag	Coverage Δ
unittests	89.41% <72.31%> (-0.18%)	⬇️

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

Files with missing lines	Coverage Δ
.../include/controller_manager/controller_manager.hpp	96.87% <ø> (ø)
controller_manager/src/controller_manager.cpp	76.38% <72.31%> (-0.32%)	⬇️

... and 3 files with indirect coverage changes

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[christophfroehlich]

works great, some minor comments

[christophfroehlich]

Nice work!