v0.18.x: Improved plotter accuracy

In #135, the adaptive plotter was improved to more accurately plot highly periodic functions, and also to avoid plotting duplicate points. This should give a quality boost to most plots, but may slightly alter some. The sampling depth parameters are now "one lower", meaning that if you were previously passing maxSamplingDepth={15}, for example, you should now pass maxSamplingDepth={16}. Change is annoying, but the depth made no sense before, and now it does (a depth of 16 means 2¹⁶ subdivisions).

In this janky screenshot of a visual regression test, you can see the improved density of sin(1/x).