[fix][evaluation] expose async target record while processing

[caijialin0626]

What

• Backfill processing turn results with TargetResultID from turn run logs.
• Allow experiment result payloads to include target_record/logid/trace_id while async target items are still processing.

Verification

• go test ./modules/evaluation/domain/service -run TestExptResultServiceImpl_MGetExperimentResult_FillsProcessingTargetRecordFromRunLog
• go test ./modules/evaluation/domain/service -run TestExptResultServiceImpl_MGetExperimentResult
• E2E PPE experiment 7590096217044173570 shows two processing rows with distinct target_logid values.

[codecov]

Codecov Report

❌ Patch coverage is 83.92857% with 9 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...ules/evaluation/domain/service/expt_result_impl.go	83.92%	4 Missing and 5 partials ⚠️

@@            Coverage Diff             @@
##             main     #533      +/-   ##
==========================================
+ Coverage   77.33%   77.39%   +0.06%     
==========================================
  Files         657      657              
  Lines       73826    73871      +45     
==========================================
+ Hits        57091    57171      +80     
+ Misses      13346    13306      -40     
- Partials     3389     3394       +5     

Flag	Coverage Δ
unittests	77.39% <83.92%> (+0.06%)	⬆️

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

Files with missing lines	Coverage Δ
...ules/evaluation/domain/service/expt_result_impl.go	75.17% <83.92%> (+2.52%)	⬆️

... and 1 file with indirect coverage changes

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