Remove circular dependency between MeasurementResult and M gate

[BrunoLiegiBastonLiegi]

This should close #1433

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 99.94%. Comparing base (68bdb98) to head (21f0d7e).
Report is 27 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1465   +/-   ##
=======================================
  Coverage   99.94%   99.94%           
=======================================
  Files          81       81           
  Lines       11740    11740           
=======================================
  Hits        11733    11733           
  Misses          7        7           

Flag	Coverage Δ
unittests	99.94% <100.00%> (ø)

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[stavros11]

Thanks @BrunoLiegiBastonLiegi, good catch.

[MatteoRobbiati]

Thanks!