Add support for query-time search parameters in SEARCH statements

[srimon12]

• added EXACT support for exact KNN search
• added WITH { hnsw_ef, exact, acorn } for query-time Qdrant search params
• wired search params through dense and hybrid search execution
• added tests and README updates

[srimon12]

Fixes the hybrid-search compatibility issue we hit locally.

Summary:

• Dense SEARCH now works against hybrid/named-vector collections by explicitly querying the "dense" vector when the collection is hybrid-shaped.
• Reranking is now compatible with both fastembed package layouts, and the default reranker model matches what the installed fastembed build actually supports.
• CLI help text was updated to reflect the already-supported EXACT / WITH search syntax.
• Added a regression test for dense search against hybrid collections.

Why this change:
A plain dense SEARCH on a hybrid collection was failing with Qdrant’s Not existing vector name error because the executor was not specifying using="dense" for named-vector collections. While validating that fix live, reranking also exposed a fastembed compatibility issue in my environment, so that was fixed in the same focused patch.

Verification:

• pytest -q → 213 passed
• confirmed locally against the connected Qdrant instance that dense search on a hybrid collection now succeeds
• confirmed the rerank path also works after the fastembed compatibility fix

[pavanjava]

Awesome and thanks for the contribution.