extractXYPlaneSections: option to use or not the tree

[Fedr]

[[nodiscard]] MRMESH_API PlaneSections extractXYPlaneSections( const MeshPart & mp, float zLevel, UseAABBTree u = UseAABBTree::Yes );
[[nodiscard]] MRMESH_API bool hasAnyXYPlaneSection( const MeshPart & mp, float zLevel, UseAABBTree u = UseAABBTree::Yes );