feat: add DocsFilter read path

[forshev]

Description

Add read path methods to DocsFilter

---

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 53.64807% with 108 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.09%. Comparing base (6ce5f40) to head (c9f85f5).

Files with missing lines	Patch %	Lines
filtermanager/loader.go	56.47%	19 Missing and 18 partials ⚠️
filtermanager/filter_manager.go	0.00%	35 Missing ⚠️
filtermanager/iterator_asc.go	65.78%	10 Missing and 3 partials ⚠️
filtermanager/iterator_desc.go	63.88%	10 Missing and 3 partials ⚠️
filtermanager/merged_iterator.go	33.33%	8 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #375      +/-   ##
==========================================
- Coverage   70.32%   70.09%   -0.24%     
==========================================
  Files         214      219       +5     
  Lines       16055    16288     +233     
==========================================
+ Hits        11291    11417     +126     
- Misses       3951     4032      +81     
- Partials      813      839      +26     

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