perf(skip masks): skip masks as roaring bitmaps in fetch

[forshev]

Description

Read skip masks as roaring bitmap for fetch

Fixes #420

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 70.83333% with 35 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.66%. Comparing base (5647ba2) to head (a750a36).

Files with missing lines	Patch %	Lines
skipmaskmanager/loader.go	52.94%	11 Missing and 5 partials ⚠️
skipmaskmanager/encoding.go	58.33%	10 Missing ⚠️
skipmaskmanager/skip_mask_manager.go	84.37%	3 Missing and 2 partials ⚠️
frac/active_index.go	85.71%	1 Missing ⚠️
skipmaskmanager/iterator_asc.go	83.33%	1 Missing ⚠️
skipmaskmanager/iterator_desc.go	83.33%	1 Missing ⚠️
skipmaskmanager/merged_iterator.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #421   +/-   ##
=======================================
  Coverage   70.65%   70.66%           
=======================================
  Files         219      219           
  Lines       17023    17059   +36     
=======================================
+ Hits        12028    12055   +27     
- Misses       4096     4102    +6     
- Partials      899      902    +3     

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