Add Pen and Path tool modes to avoid showing all handles (#2264)

* Path tool only show frontier overlays

* Implemented all modes for pen and path tool

* Fixed formatting issue

* Changes in selection behaviour of handles

* Selection toggle only on drag not click

* Changed comment

* Code review

---------

Co-authored-by: Keavon Chambers <keavon@keavon.com>

node-graph/gcore/src/vector/vector_data.rs

@@ -293,6 +293,26 @@ impl VectorData {
 			None
 		}
 	}
+
+	pub fn adjacent_segment(&self, manipulator_id: &ManipulatorPointId) -> Option<(PointId, SegmentId)> {
+		match manipulator_id {
+			ManipulatorPointId::PrimaryHandle(segment_id) => {
+				// For start handle, find segments ending at our start point
+				let (start_point_id, _, _) = self.segment_points_from_id(*segment_id)?;
+				let start_index = self.point_domain.resolve_id(start_point_id)?;
+
+				self.segment_domain.end_connected(start_index).find(|&id| id != *segment_id).map(|id| (start_point_id, id))
+			}
+			ManipulatorPointId::EndHandle(segment_id) => {
+				// For end handle, find segments starting at our end point
+				let (_, end_point_id, _) = self.segment_points_from_id(*segment_id)?;
+				let end_index = self.point_domain.resolve_id(end_point_id)?;
+
+				self.segment_domain.start_connected(end_index).find(|&id| id != *segment_id).map(|id| (end_point_id, id))
+			}
+			ManipulatorPointId::Anchor(_) => None,
+		}
+	}
 }
 
 impl Default for VectorData {