This PR adds the *Line Hide* tool and the corresponding
`PAINT_OT_hide_show_line_gesture` operator to Sculpt Mode.
*Line Hide* supports common modal functionality including:
* Snapping to angles
* Flipping the selection area
* Moving selection area
Addresses one of the tools in #80390
Pull Request: https://projects.blender.org/blender/blender/pulls/119671