Fair Tangency and Fair Positions as geometry nodes

Add the two fairing algorithms from sculpt mode into geometry nodes.

It could have two simple inputs:

Selection - This is necessary to define which vertices get smoothed out, just like how you select a face set in sculpt mode. Without any input the node doesn't have any effect.

Factor - The strength of the effect, soft capped between 0 and 1. Any values outside of this range extrapolates the effect in either direction.

The Fair Positions node would have the same inputs.

Before: After:

Use cases - The fairing algorithms are very effective at smoothing out parts of a mesh in a very clean way, and having this effect as a node will open up a lot of possibilities for procedural modeling.

One example that inspired this proposal is that I need to smooth out the hair tufts from my character as shown in the pictures above, but since the Fair Tangency is only available in sculpt mode there is no way of doing it after all the deformations from armature, corrective smoothing and subdivision surface are already done. With the node I would be able to remove the tufts very easily by using a vertex group and the result would be super clean.