[Feature](lance) Add vector and scalar index lifecycle management

Parent

Tracked by #66340. #65730 provides read-only index consumption and automatic vector-index selection.

Scope

• Create vector indexes.
• Create scalar indexes.
• Show the number of indexes.
• Show index names, UUIDs, columns, types, and dataset versions.
• Replace or rebuild an index with the same name.
• Drop indexes by name.
• Define authorization, concurrency, versioning, failure recovery, and metadata refresh semantics.

Completion criteria

• FE statements and metadata APIs are implemented.
• BE or service-side index operations are integrated with Lance.
• Unit and regression tests cover create, inspect, replace, rebuild, drop, and failures.
• User documentation describes syntax, lifecycle semantics, and limitations.
• The behavior is verified for vector and scalar index types.