engine: use PEP 604 syntax for optionals/unions (#10072)

[SpecLad]

Motivation and context

This is a continuation of #10060.

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)

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.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov-commenter]

Codecov Report

❌ Patch coverage is 98.36066% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 82.57%. Comparing base (5cc1e98) to head (06d114a).
⚠️ Report is 3 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #10087      +/-   ##
===========================================
+ Coverage    74.62%   82.57%   +7.94%     
===========================================
  Files          428      428              
  Lines        46252    46238      -14     
  Branches      4139     4139              
===========================================
+ Hits         34517    38181    +3664     
+ Misses       11735     8057    -3678     

Components	Coverage Δ
cvat-ui	77.62% <ø> (+0.16%)	⬆️
cvat-server	86.77% <98.36%> (+14.55%)	⬆️

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