Geometry Nodes: Improve UV Sphere primive performance

In a test producing 10 million vertices I observed a 3.6x improvement,
from 470ms to 130ms. The largest improvement comes from calculating
each mesh array on a separate thread. Besides that, the larger changes
come from splitting the filling of corner and face arrays, and
precalculating sines and cosines for each ring.

Using `parallel_invoke` does gives some overhead. On a small 32x16
input, the time went up from 51us to 74us. It could be disabled
for small outputs in the future. The reasoning for this parallelization
method instead of more standard data-size-based parallelism is that the
latter wouldn't be helpful except for very high resolution.

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