test: improve coverage of predictive controller constraint violation

[franckgaga]

Similarly to the new tests in #387, this PR adds tests for constraint violations on two LinMPC controllers:

1. Only hard constraints with Cwt=Inf
2. Only soft constraints withCwt=1e5

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.60%. Comparing base (021349a) to head (47e531c).
⚠️ Report is 6 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #388   +/-   ##
=======================================
  Coverage   98.60%   98.60%           
=======================================
  Files          27       27           
  Lines        5595     5595           
=======================================
  Hits         5517     5517           
  Misses         78       78           

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