align contact frame to cylinder for sphere-cylinder side collisions

[david-wb]

This proposed change makes it so that when the side of a cylinder is in contact with a sphere, the contact frame is aligned to the axis of the cylinder. Otherwise, the contact frame seems to have arbitrary alignment because the code simulates a virtual sphere-sphere collision which zeros-out the second axis in the contact frame. The motivation for this change is to make it easier to simulate anisotropic friction on cylinders in contact with spheres. I also opened a discussion about this here, but it is so far unanswered:

Before (inconsistent contact frame alignment):

After (x-axis of contact frame aligned to z-axis of the cylinder):

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