Added test for opacity reset

[klakhov]

Motivation and context

Cypress test for #7186 #7176

How has this been tested?

Checklist

• I submit my changes into the develop branch
• [ ] I have created a changelog fragment
• [ ] I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues (see GitHub docs)
• I have increased versions of npm packages if it is necessary
  (cvat-canvas,
  cvat-core,
  cvat-data and
  cvat-ui)

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.

[codecov]

Codecov Report

Merging #7207 (87df6a4) into develop (946fb90) will increase coverage by 0.00%.
Report is 1 commits behind head on develop.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #7207   +/-   ##
========================================
  Coverage    81.47%   81.47%           
========================================
  Files          365      365           
  Lines        39892    39918   +26     
  Branches      3700     3703    +3     
========================================
+ Hits         32503    32525   +22     
- Misses        7389     7393    +4     

Components	Coverage Δ
cvat-ui	75.48% <ø> (-0.01%)	⬇️
cvat-server	87.10% <ø> (+<0.01%)	⬆️

[bsekachev]

Let's merge