Should node finding use Newton or Gauss-Newton?

[inducer]

Upsides of Gauss-Newton:

• More robust?
• Gives us "the closest" if the exact point can't be found

Downside:

• Conditioning penalty via the normal equations

https://github.com/inducer/meshmode/blob/dd247039a027e9b75417e4fdddf8cc4c608b6622/meshmode/discretization/connection/opposite_face.py#L136-L153

cc @xywei @alexfikl @majosm