Improve unpack_bits

[svilupp]

• Improved the implementation of RAGTools.unpack_bits to be faster with fewer allocations (relevant for BitPackedCosineSimilarity)

[codecov]

Codecov Report

Attention: Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 92.43%. Comparing base (eff6682) to head (61468e8).

Files	Patch %	Lines
src/Experimental/RAGTools/utils.jl	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #165      +/-   ##
==========================================
- Coverage   92.53%   92.43%   -0.10%     
==========================================
  Files          44       44              
  Lines        3605     3571      -34     
==========================================
- Hits         3336     3301      -35     
- Misses        269      270       +1     

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