Currently there is no way to flip normals in geometry nodes. This node
makes that possible by flipping the winding order of selected faces.
The node is purposely not called "Flip Normals", because normals are
derived data, changing them is only a side effect. The real change is
that the vertex and edge indices in the face corners of every selected
polygon are reversed, and face corner attribute data is reversed.
While there are existing utilities to flip a polygon and its custom
data, this node aims to process an attribute's data together instead
of processing all attributes separately for each index.
Differential Revision: https://developer.blender.org/D13809
c39d514a4e