[Feature](lance) Support multi-vector columns and queries

[Gabriel39]

Parent

Tracked by #66340. Single-vector search was introduced by #65730.

Scope

• Map List<FixedSizeList<...>> Lance columns for multi-vector use.
• Accept multiple sub-vectors in one logical query.
• Implement Multi-vector Search.
• Define aggregation, scoring, filtering, Top-K, and _distance semantics.
• Do not implicitly expand the scope to joint search across multiple vector columns.

Completion criteria

• FE type analysis, serialization, and BE execution are implemented.
• Tests cover supported element types, dimensions, nullability, and scoring behavior.
• User documentation describes the query format and result semantics.
• Representative multi-vector datasets and indexes are verified.