Undirected line-tangent-to-circle constraint

[adamchalmers]

Right now the LineTangentToCircle cares about the line's direction.

    /// This line must be tangent to the circle
    /// (i.e. touches its perimeter in exactly one place)
    /// Note this constraint is directional: making circle C
    /// tangent to PQ will produce a different solution to QP.
    LineTangentToCircle(LineSegment, Circle),

But this is confusing UX -- users don't draw their line segments with a direction. The constraint should not care about direction either. When there are two possible solutions, it should just choose the solution closest to the user's initial guess.

[nickmccleery]

Here's a python sketch for a non-directional implementation:

KittyCAD/geometric-constraint-playground#13