Improving differential_transmission configure checks

[jordan-palacios]

Current version fails in our setup where some actuator interfaces are exposed with no corresponding joint interface (intended).

This PR rewrites some of the configure check to allow this situation. Also, we add another check to make sure there is at least one valid joint-actuator handle pair.

[codecov]

Codecov Report

❌ Patch coverage is 85.41667% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.62%. Comparing base (fc77935) to head (3473218).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...ansmission_interface/differential_transmission.hpp	78.78%	6 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2812   +/-   ##
=======================================
  Coverage   89.61%   89.62%           
=======================================
  Files         152      152           
  Lines       17774    17816   +42     
  Branches     1460     1455    -5     
=======================================
+ Hits        15929    15967   +38     
- Misses       1253     1263   +10     
+ Partials      592      586    -6     

Flag	Coverage Δ
unittests	89.62% <85.41%> (+<0.01%)	⬆️

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

Files with missing lines	Coverage Δ
..._interface/test/differential_transmission_test.cpp	99.60% <100.00%> (+0.02%)	⬆️
...ansmission_interface/differential_transmission.hpp	75.94% <78.78%> (+2.61%)	⬆️

... and 1 file with indirect coverage changes

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[saikishor]

Thanks for the fix!

[christophfroehlich]

Thanks, LGTM