Space when dragging to shift what's being drawn

For anything that can be dragged with the mouse clicked down, Space should offset it while held down. We have this in a few places (like dragging the next preview segment in the Pen tool), but it should be universal across all dragging actions in every tool.

- Select tool:
- [ ] Transform cage resizing, skewing, and rotating
- [ ] Box and lasso area selection
- Artboard tool:
- [ ] Artboard drawing and resizing
- Gradient tool:
- [ ] Gradient line drawing and endpoint moving
- Path tool:
- [ ] Box and lasso area selection
- Line tool:
- [ ] Line drawing and endpoint moving
- Rectangle/Ellipse/Polygon tools:
- [ ] New shape drawing (and resizing after #1715)
- Text tool:
- [ ] Text area drawing and resizing
- And in the node graph:
- [ ] Box (and lasso after #2532) area selection

まず、Pen ツールの次のプレビューセグメントをドラッグしたときの既存の Space の動作を調べ、続いて、列挙されている各ツールでドラッグがどのように処理されるかを追跡します。動作を Select、Artboard、Gradient、Path、Line、shape、Text、node graph の各アクションに拡張し、Space を押している間、チェックリストの各項目でドラッグしたコンテンツがオフセットされることを確認します。

索引モデルが issue の本文から書いたものです。