Geometry Nodes: new Scale Elements nodes

This node can scale individual edges and faces. When multiple selected
faces/edges share the same vertices, they are scaled together.
The center and scaling factor is averaged in this case.

For some examples see D13757.

Differential Revision: https://developer.blender.org/D13757

release/scripts/startup/nodeitems_builtins.py

@@ -150,6 +150,7 @@ def mesh_node_items(context):
     yield NodeItem("GeometryNodeSubdivideMesh")
     yield NodeItem("GeometryNodeSubdivisionSurface")
     yield NodeItem("GeometryNodeTriangulate")
+    yield NodeItem("GeometryNodeScaleElements")
     yield NodeItemCustom(draw=lambda self, layout, context: layout.separator())
     yield NodeItem("GeometryNodeInputMeshEdgeAngle")
     yield NodeItem("GeometryNodeInputMeshEdgeNeighbors")