This PR adds the `Pen Tool` to `Curves` objects. The logic and keybinds are shared with the Grease Pencil `Pen Tool` Unlike the legacy pen tool, this version can works with multiple objects. Note: Some changes have been made from the legacy curve object's pen tool. A list of changes can be found at #142646 Pull Request: https://projects.blender.org/blender/blender/pulls/144833