Sculpt: Option to limit the action of line gestures to the segment

This adds a tool property for sculpt line gesture tools (line and
project) to limits its effect to the segment of the gesture instead of
using the infinite line to bisect the mesh in two parts.

To achieve that, the line gesture now has two extra side planes that can
be enabled/disabled for getting the nodes from the PBVH and to test the
vertices.

Reviewed By: sergey

Differential Revision: https://developer.blender.org/D9307

release/scripts/startup/bl_ui/space_toolsystem_toolbar.py

@@ -1259,6 +1259,7 @@ class _defs_sculpt:
         def draw_settings(_context, layout, tool):
             props = tool.operator_properties("paint.mask_line_gesture")
             layout.prop(props, "use_front_faces_only", expand=False)
+            layout.prop(props, "use_limit_to_segment", expand=False)
 
         return dict(
             idname="builtin.line_mask",
@@ -1331,12 +1332,17 @@ class _defs_sculpt:
 
     @ToolDef.from_fn
     def project_line():
+        def draw_settings(_context, layout, tool):
+            props = tool.operator_properties("sculpt.project_line_gesture")
+            layout.prop(props, "use_limit_to_segment", expand=False)
+
         return dict(
             idname="builtin.line_project",
             label="Line Project",
             icon="ops.sculpt.line_project",
             widget=None,
             keymap=(),
+            draw_settings=draw_settings,
         )
 
     @ToolDef.from_fn