Allowing to set not trainable gates parameters

[BrunoLiegiBastonLiegi]

Addresses #1699

Checklist:

• Reviewers confirm new code works as expected.
• Tests are passing.
• Coverage does not decrease.
• Documentation is updated.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.15%. Comparing base (9d4c453) to head (f91f5dd).
⚠️ Report is 866 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1701   +/-   ##
=======================================
  Coverage   99.15%   99.15%           
=======================================
  Files          80       80           
  Lines       12727    12729    +2     
=======================================
+ Hits        12620    12622    +2     
  Misses        107      107           

Flag	Coverage Δ
unittests	99.15% <100.00%> (+<0.01%)	⬆️

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