[Transmissions] Make transmission interface work with new variants approach

[saikishor]

The new changes to the handles, that the data exists inside the Handle itself will create problems with the old transmission_interface API and it is kinda dysfunctional with the new approach. This PR aims to solve the issue by migrating the transmission part to the new API and making it functional with the latest shared pointers approach.

[codecov]

Codecov Report

Attention: Patch coverage is 96.00000% with 16 lines in your changes missing coverage. Please review.

Project coverage is 88.08%. Comparing base (5dbd6d5) to head (9fa9b18).
Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
...ce/include/transmission_interface/transmission.hpp	0.00%	9 Missing ⚠️
...ude/transmission_interface/simple_transmission.hpp	72.72%	1 Missing and 2 partials ⚠️
...ansmission_interface/differential_transmission.hpp	92.59%	0 Missing and 2 partials ⚠️
...ission_interface/four_bar_linkage_transmission.hpp	90.00%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1845      +/-   ##
==========================================
- Coverage   88.25%   88.08%   -0.17%     
==========================================
  Files         121      121              
  Lines       12301    12459     +158     
  Branches     1093     1101       +8     
==========================================
+ Hits        10856    10975     +119     
- Misses       1051     1088      +37     
- Partials      394      396       +2     

Flag	Coverage Δ
unittests	88.08% <96.00%> (-0.17%)	⬇️

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

Files with missing lines	Coverage Δ
...erface/include/transmission_interface/accessor.hpp	83.33% <ø> (ø)
..._interface/test/differential_transmission_test.cpp	99.53% <100.00%> (+0.15%)	⬆️
...erface/test/four_bar_linkage_transmission_test.cpp	99.52% <100.00%> (+0.13%)	⬆️
...ission_interface/test/simple_transmission_test.cpp	100.00% <100.00%> (ø)
transmission_interface/test/utils_test.cpp	100.00% <100.00%> (ø)
...ansmission_interface/differential_transmission.hpp	70.68% <92.59%> (-9.12%)	⬇️
...ission_interface/four_bar_linkage_transmission.hpp	68.22% <90.00%> (-9.68%)	⬇️
...ude/transmission_interface/simple_transmission.hpp	69.09% <72.72%> (-5.42%)	⬇️
...ce/include/transmission_interface/transmission.hpp	9.09% <0.00%> (-90.91%)	⬇️

... and 2 files with indirect coverage changes