feat: implement steward-ward pattern for schedule and dispatch goroutines

[svaloumas]

• Adds Scheduler.NewSteward method
• Turns Scheduler.Dispatch and Scheduler.Schedule methods to wards
• Refactors WorkService.Dispatch method

[codecov]

Codecov Report

❌ Patch coverage is 59.77654% with 72 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.74%. Comparing base (732aec4) to head (9ed3ebc).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/core/service/schedulersrv/service.go	65.67%	45 Missing and 1 partial ⚠️
internal/core/service/worksrv/service.go	29.72%	26 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #13      +/-   ##
==========================================
- Coverage   76.73%   75.74%   -1.00%     
==========================================
  Files          32       32              
  Lines        3271     3360      +89     
==========================================
+ Hits         2510     2545      +35     
- Misses        538      593      +55     
+ Partials      223      222       -1     

Flag	Coverage Δ
unittests	75.74% <59.77%> (-1.00%)	⬇️

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