Cone graph object: make the cone angle a configurable attribute

Use case:
In metrology, a cone plot can be used to represent the vectors for each point taken on a surface by a coordinate measuring machine or similar instrument
At moderate point densities and higher, the overlap between the bases of the cones makes the plot unreadable unless the cone size is dialled all the way down (in turn making the vectors' direction hard to distinguish).

Proposed solution:
Have the cone angle driven by a user-configurable attribute (with set limits) allowing for slimmer or fatter cones accordingly to the user’s needs.
Ideally a cone angle of 0 should be allowed to effectively transform the cone to a line of the same length, but this is a less critical point.

まずコーングラフオブジェクトのスキーマとレンダリング実装を見つけ、次に既存のコーンサイズ属性と関連するテストを調べます。ユーザーが上限と下限のあるコーン角度を設定でき、可能であれば要求されたゼロ角度の動作にも対応し、サポートされる範囲の限界でも可視化が有効なままであれば完了です。