Add filtered ANN adapter support

[dovinmu]

What changed

• implement the current numeric-filter preparation contract for Antfly, Chroma, Elasticsearch, Qdrant, and Weaviate
• send native Antfly filter_query clauses with vector searches and ingest scalar filter fields
• support local exact filtered-neighbor artifacts when the declared upstream dataset file is unavailable
• expose the adapter knobs required by the focused filtered-ANN harness

Why

The Circus filtered-ANN benchmark needs comparable pre-filtered vector searches across engines, with exact recall and nDCG ground truth. The published OpenAI 50K integer-filter case declares a neighbor artifact that is currently absent from the public bucket, so the harness must be able to supply the exact artifact generated locally.

Impact

This is the adapter dependency for a separate filtered-ANN benchmark in antfly-circus. It does not turn filtered and regular ANN into the same result track.

Validation

• VectorDBBench Antfly adapter tests
• filtered adapter contract tests
• live Antfly numeric-range filter smoke test
• completed 50K filtered matrix across Antfly, Weaviate, Elasticsearch, Milvus, pgvector, and Chroma