WIP: More signatures

[okurz]

• Simplify Resource::Locks with direct return of boolean calculations
• Use signatures in Resource::Locks
• Slightly simplify script/openqa-validate-yaml
• Use signatures in WebAPI::ServerSideDataTable
• Use signatures in Resource::Jobs

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 98.39%. Comparing base (1a01d2d) to head (b295d47).
Report is 771 commits behind head on master.

Files with missing lines	Patch %	Lines
script/openqa-validate-yaml	0.00%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5511   +/-   ##
=======================================
  Coverage   98.38%   98.39%           
=======================================
  Files         391      391           
  Lines       37883    37874    -9     
=======================================
- Hits        37271    37265    -6     
+ Misses        612      609    -3     

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[mergify]

This pull request is now in conflicts. Could you fix it? 🙏