This commit ports the fillet curves node to the new curves data-block,
and moves the fillet node implementation to the geometry module to help
separate the implementation from the node.
The changes are similar to the subdivide node or resample node. I've
resused common utilities where it makes sense, though some things like
the iteration over attributes can be generalized further. The node
is now multi-threaded per-curve and inside each curve, and some buffers
are reused per curve to avoid many allocations.
The code is more explicit now, and though there is more boilerplate to
pass around many spans, the more complex logic should be more readable.
Differential Revision: https://developer.blender.org/D15346
The ported normal calculation from ceed37fc5c neglected to
use the tilt attribute to rotate the normals around the tangents.
This commit adds that behavior back, adding a new math header file
to avoid duplicating the rotation function for normalized axes.
Differential Revision: https://developer.blender.org/D14655
