feat: LEAP-1720: distinguish annotations created using Bulk Labeling

[triklozoid]

• added bulk_created flag for annotation model

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.78%. Comparing base (d7cebed) to head (133f704).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #6821   +/-   ##
========================================
  Coverage    76.78%   76.78%           
========================================
  Files          171      171           
  Lines        14023    14024    +1     
========================================
+ Hits         10767    10768    +1     
  Misses        3256     3256           

Flag	Coverage Δ
pytests	76.78% <100.00%> (+<0.01%)	⬆️

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