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 99.50%. Comparing base (b0c2acd) to head (3cae0d5).
⚠️ Report is 90 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1701   +/-   ##
=======================================
  Coverage   99.50%   99.50%           
=======================================
  Files          78       78           
  Lines       13674    13676    +2     
=======================================
+ Hits        13606    13608    +2     
  Misses         68       68           

Flag	Coverage Δ
unittests	99.50% <100.00%> (+<0.01%)	⬆️

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