Fix flaky transmission_interface tests by making them deterministic. (backport #1665)

[mergify]

Fixes #1555

The transmission_interface tests would give non deterministic spurious failures. The non determinism was because tests were randomly generated using the system time to seed the random number generator. The spurious failures were due to occasionally occurring tiny rounding errors from floating point math.

By seeding the random number generator the tests become deterministic and we avoid the spurious failures.
Additionally, changing the order of some of the multiplications seems to reduce the rounding error.

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This is an automatic backport of pull request #1665 done by [Mergify](https://mergify.com).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.45%. Comparing base (ae2ed7c) to head (31221b9).
Report is 15 commits behind head on iron.

Additional details and impacted files

@@            Coverage Diff             @@
##             iron    #1671      +/-   ##
==========================================
- Coverage   87.45%   87.45%   -0.01%     
==========================================
  Files         101      101              
  Lines        8078     8081       +3     
  Branches      711      711              
==========================================
+ Hits         7065     7067       +2     
- Misses        717      718       +1     
  Partials      296      296              

Flag	Coverage Δ
unittests	87.45% <100.00%> (-0.01%)	⬇️

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

Files	Coverage Δ
...ission_interface/four_bar_linkage_transmission.hpp	78.57% <100.00%> (ø)
...smission_interface/test/random_generator_utils.hpp	100.00% <100.00%> (ø)