feat: finish initial implementation of IterSubjects

[barakmich]

Description

Testing

References

[codecov]

Codecov Report

❌ Patch coverage is 72.50996% with 69 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.43%. Comparing base (9171c3f) to head (38eb832).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/query/arrow.go	61.71%	13 Missing and 5 partials ⚠️
pkg/query/union.go	55.56%	10 Missing and 6 partials ⚠️
pkg/query/exclusion.go	82.86%	6 Missing and 6 partials ⚠️
pkg/query/intersection.go	76.00%	6 Missing and 6 partials ⚠️
pkg/query/intersection_arrow.go	78.73%	5 Missing and 5 partials ⚠️
pkg/query/datastore.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2809      +/-   ##
==========================================
- Coverage   78.52%   78.43%   -0.09%     
==========================================
  Files         459      459              
  Lines       44448    44662     +214     
==========================================
+ Hits        34898    35025     +127     
- Misses       6723     6777      +54     
- Partials     2827     2860      +33     

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[tstirrat15]

LGTM. see comments

[tstirrat15]

LGTM