MB-69881: Updated interfaces for more performant vector search

[CascadingRadium]

• Replace slice-based eligible document access with an iterator-based abstraction (EligibleDocumentList / EligibleDocumentIterator), enabling storage-layer streaming/visitor-style consumption of eligible docIDs, eliminating intermediate materialization, and decoupling retrieval from underlying eligible-document storage representations.

[Copilot]

Pull request overview

This pull request refactors vector search to use an iterator-based abstraction for accessing eligible documents, replacing the previous slice-based approach. The changes introduce two new interfaces (EligibleDocumentIterator and EligibleDocumentList) and modify the EligibleDocumentSelector interface to support streaming access patterns, eliminating the need for intermediate materialization of eligible document IDs.

Key Changes:

• Introduced EligibleDocumentIterator interface for streaming document ID iteration
• Introduced EligibleDocumentList interface as a container providing both iterator access and count information
• Modified EligibleDocumentSelector.SegmentEligibleDocs() to return EligibleDocumentList instead of []uint64

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

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