Update RAG performance (Breaking changes)

[svilupp]

Breaking Changes

• The return type of RAGTools.find_tags(::NoTagger,...) is now ::Nothing instead of CandidateChunks/MultiCandidateChunks with all documents.
• Base.getindex(::MultiIndex, ::MultiCandidateChunks) now always returns sorted chunks for consistency with the behavior of other getindex methods on *Chunks.

Updated

• Cosine similarity search now uses partialsortperm for better performance on large datasets.
• Skip unnecessary work when the tagging functionality in the RAG pipeline is disabled (find_tags with NoTagger always returns nothing which improves the compiled code).
• Changed the default behavior of getindex(::MultiIndex, ::MultiCandidateChunks) to always return sorted chunks for consistency with other similar functions. Note that you should always use re-rankering anyway (see FlashRank.jl).

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 92.53%. Comparing base (c5ac64f) to head (2996efb).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #164 +/- ## ========================================== - Coverage 92.62% 92.53% -0.10% ========================================== Files 44 44 Lines 3609 3605 -4 ========================================== - Hits 3343 3336 -7 - Misses 266 269 +3 ```

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