This commit changes the Curve to Mesh node to work with Curves
instead of CurveEval. The change ends up basically completely
rewriting the node, since the different attribute storage means that
the decisions made previously don't make much sense anymore.

The main loops are now "for each attribute: for each curve combination"
rather than the other way around, with the goal of taking advantage
of the locality of curve attributes. This improvement is quite noticeable
with many small curves; I measured a 4-5x improvement (around 4-5s
to <1s) when converting millions of curves to tens of millions of faces.
I didn't obverse any change in performance compared to 3.1 with fewer
curves though.

The changes also solve an algorithmic flaw where any interpolated
attributes would be evaluated for every curve combination instead
of just once per curve. This can be a large improvement when there
are many profile curves.

The code relies heavily on a function called foreach_curve_combination
which calculates some basic information about each combination and
calls a templated function. I made some assumptions there about
unnecessary information gathering being removed with compiler optimizations.
For further performance improvements in the future that might be
an area to investigate. Another might be using a "for a group of curves:
for each attribute: for each curve" pattern to increase the locality of
memory access.