fix(#1658): align agents for predictions annotations

[frascuchon]

This PR includes changes related to #1658 to align/normalize predictions/annotations keys with the agent fields:

• For the prediction field, agents will be computed from the key
• For the predictions field, agents will be set to None

[codecov]

Codecov Report

Base: 94.97% // Head: 95.02% // Increases project coverage by +0.04% 🎉

Coverage data is based on head (b30899f) compared to base (8588972).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@               Coverage Diff                @@
##           releases/0.x    #1742      +/-   ##
================================================
+ Coverage         94.97%   95.02%   +0.04%     
================================================
  Files               148      148              
  Lines              6812     6815       +3     
================================================
+ Hits               6470     6476       +6     
+ Misses              342      339       -3     

Flag	Coverage Δ
pytest	95.02% <100.00%> (+0.04%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/rubrix/server/daos/models/records.py	97.05% <100.00%> (+0.08%)	⬆️
...ubrix/labeling/text_classification/label_errors.py	90.36% <0.00%> (+3.61%)	⬆️

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