feat: include feedback labels in CTR dataset

[zhangzhenghao]

Summary

• Add feedback labels as CTR/FM context labels when loading datasets from the data store
• Preserve labels from the latest feedback for each user-item sample across positive, explicit negative, and read feedback
• Cover feedback context labels in master dataset loading tests

Test Plan

• go test ./master -run 'TestMaster/TestLoadDataFromDatabase$' -count=1
• go test ./model/ctr -run 'TestDataset|TestSplit|TestLoad' -count=1
• git diff --check

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.78%. Comparing base (080092c) to head (a805c47).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1291      +/-   ##
==========================================
- Coverage   74.16%   73.78%   -0.39%     
==========================================
  Files          92       92              
  Lines       17257    17278      +21     
==========================================
- Hits        12799    12748      -51     
- Misses       3148     3185      +37     
- Partials     1310     1345      +35     

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